What are the factors used by the courts to determine the length of a sentence in a sexual assault case?

"When a judgment of imprisonment is to be imposed and the statute specifies three possible terms, the choice of the appropriate term shall rest within the sound discretion of the court. ... The court shall select the term which, in the court's discretion, best serves the interests of justice. The court shall set forth on the record the reasons for imposing the term selected ...." ( 1170, subd. (b).) Insofar as imposition of the upper term is concerned, "[a]n aggravating circumstance is a fact that makes the offense distinctively worse than the ordinary. [Citations.] Aggravating circumstances include those listed in the sentencing rules, as well as any facts statutorily declared to be circumstances in aggravation [citation] and any other facts that are reasonably related to the decision being made. [Citation.]" ( People v. Black (2007) 41 Cal.4th 799, 817, 62 Cal.Rptr.3d 569, 161 P.3d 1130 ; see Rules 4.408(a), 4.421.)