23 The applicant contends that the term of 7 years' imprisonment is too long. The thrust of the submissions put on his behalf were to the effect that the sentencing Judge's starting point of 12 years was too high and should have been in the range of 9 to 11 years; that having regard to what was said to be appropriate percentage deductions for the plea of guilty and forfeiture of assets, the sentencing range is reduced to 5 to 6 years. This mathematical approach of subtracting specific amounts for particular mitigating factors has been criticised by the High Court in Wong (supra) and Markarian v The Queen [2005] HCA 25; (2005) 79 ALJR 1048 at [39] per Gleeson CJ, Gummow, Hayne and Callinan JJ. It is an improper fetter on the exercise of the sentencing discretion and is based on the inaccurate assumption that there is a single correct sentence. In order to be successful, the applicant must establish that the sentence of 7 years is manifestly excessive. In determining whether a sentence is manifestly excessive (in the absence of express error), the steps by which the trial Judge reached his conclusion as to the appropriate sentence are irrelevant. The central question is whether, having regard to all relevant sentencing considerations, the sentence is plainly unjust or unreasonable The yardsticks by which that assessment is to be made are set out in Chan. One of them is the standards of sentencing customarily observed with respect to the relevant crime. When considering that matter, it is necessary to use a common standard, be it the sentences that would have been imposed before or after the commencement of the Sentencing Amendment Act. At this stage it is still convenient to use pre-amendment sentences for comparison purposes.