Defendant first argues that the trial court erred in admitting the confession made to the FBI agents on 7 October 1981, on the grounds that the confession was not voluntarily made. Defendant concedes that the trial court’s finding of fact that defendant was not intoxicated or drugged at the time the statement was made is binding on appeal if supported by competent evidence. State v. Oxendine, 303 N.C. 235, 278 S.E. 2d 200 (1981). There was ample evidence to support the trial court’s finding that defendant was not under the influence of drugs on 7 October 1981, in the form of *689the testimony of the doctor who treated defendant on 6 October 1981, the deputy sheriff and the two FBI agents.
Nevertheless, the fact that defendant made the confession is not conclusive of the question whether the confession was voluntary. Instead, the “totality of the circumstances” must be considered and these circumstances must demonstrate that the confession was voluntary. See e.g., State v. Temple, 302 N.C. 1, 273 S.E. 2d 273 (1981); State v. Stephens, 300 N.C. 321, 266 S.E. 2d 588 (1980). The burden is upon the state to demonstrate volun-tariness by a preponderance of the evidence. State v. Johnson, 304 N.C. 680, 285 S.E. 2d 792 (1982). Our appellate courts commonly consider several factors in determining whether a confession was freely given, including: (1) whether the defendant was given his Miranda warnings; (2) whether the defendant was threatened; (3) whether the defendant was promised some reward for confessing; and (4) whether the defendant appeared to understand the questions and to answer logically. See e.g., State v. Vickers, 306 N.C. 90, 291 S.E. 2d 599 (1982); State v. Whitt, 299 N.C. 393, 261 S.E. 2d 914 (1980); State v. Pagon, 64 N.C. App. 295, 307 S.E. 2d 381 (1983). Of course, these factors are neither exclusive nor exhaustive and other circumstances may be important in a particular case.
In the case at bar, the trial court in concluding that defendant voluntarily waived his right to remain silent considered evidence that defendant was read his Miranda rights and responded logically to questions by the FBI agents, and that there was no indication that defendant was threatened or promised a reward for confessing. The evidence was sufficient to carry the state’s burden, and in the absence of any rebutting circumstances tending to indicate defendant’s confession was involuntarily made, defendant’s assignment of error must be overruled.
Defendant next argues that the trial judge erred in imposing a jail term two and a half times greater than the statutory presumptive of fourteen years. The trial judge based the sentence upon a finding of two aggravating factors and no mitigating factors. Defendant argues that the trial court erred in considering his prior convictions as an aggravating factor, on the grounds that the state did not first demonstrate that defendant was either (1) not indigent at the time of the former convictions or, if in*690digent, that defendant either (2) waived counsel or (3) was represented by counsel. Defendant cites our decision in State v. Farmer, 60 N.C. App. 779, 299 S.E. 2d 842 (1983) as authority for his interpretation of the requirements of the Fair Sentencing Act. Our decision in Farmer, however, has been partially overruled by State v. Thompson, 309 N.C. 421, 307 S.E. 2d 156 (1983). In Thompson, our supreme court held that the defendant has the burden of challenging evidence of prior convictions by either an objection or a motion to suppress. Thompson also makes it clear that the defendant has the burden of stating the grounds for his objection or motion to suppress, and of proving those grounds. In the case at bar, defendant neither objected to introduction of evidence of prior convictions nor offered evidence that he was indigent and unrepresented by counsel at the time of those convictions.1
Defendant’s assignment of error must be overruled.
No error.
Judges Arnold and Eagles concur.. For offenses committed on or after 1 October 1983, G.S. 15A-980 requires the defendant to bear the burden of both objecting to evidence of prior convictions and of proving that the convictions occurred when defendant was both indigent and unrepresented by counsel.