(1) Except as otherwise provided in RCW 11.104B.180(2)(a), a unitrust rate may be:

(a) A fixed unitrust rate; or

(b) A unitrust rate that is determined for each period using:

(i) A market index or other published data; or

(ii) A mathematical blend of market indices or other published data over a stated number of preceding periods.

(2) Except as otherwise provided in RCW 11.104B.180(2)(a), a unitrust policy may provide:

(a) A limit on how high the unitrust rate determined under subsection (1)(b) of this section may rise;

(b) A limit on how low the unitrust rate determined under subsection (1)(b) of this section may fall;

(c) A limit on how much the unitrust rate determined under subsection (1)(b) of this section may increase over the unitrust rate for the preceding period or a mathematical blend of unitrust rates over a stated number of preceding periods;

(d) A limit on how much the unitrust rate determined under subsection (1)(b) of this section may decrease below the unitrust rate for the preceding period or a mathematical blend of unitrust rates over a stated number of preceding periods; or

(e) A mathematical blend of any of the unitrust rates determined under subsection (1)(b) of this section and (a) through (d) of this subsection.