(1) When a court sentences a person under ORS 164.061, 475.907, 475.924 and 475.925:
(a) The court shall use the criminal history scale of the sentencing guidelines grid of the Oregon Criminal Justice Commission to determine the sentence to impose. The sentence described in:
(A) ORS 475.925 (1) shall be determined utilizing crime category 10 of the sentencing guidelines grid.
(B) ORS 475.907 (1) and 475.925 (2) shall be determined utilizing crime category 9 of the sentencing guidelines grid.
(C) ORS 164.061 shall be determined utilizing crime category 8 of the sentencing guidelines grid.
(b)(A) Notwithstanding ORS 161.605, the court shall impose the sentence described in ORS 164.061, 475.907, 475.924 and 475.925 and may not impose a sentence of optional probation or grant a downward dispositional departure or a downward durational departure under the rules of the commission.
(B) The court may impose a sentence other than the sentence described in ORS 164.061, 475.907, 475.924 and 475.925 if the court imposes a longer term of incarceration that is otherwise required or authorized by law.
(2) A person sentenced under ORS 164.061, 475.907, 475.924 and 475.925 may not receive a reduction in the term of incarceration for appropriate institutional behavior that exceeds 20 percent of the sentence imposed.