pro·rate 
(prō-rāt, prōrāt′)
(prō-rāt, prōrāt′)v. pro·rat·ed, pro·rat·ing, pro·rates
v.tr.
To divide, distribute, or assess proportionately.
v.intr.
To settle affairs on the basis of proportional distribution.
[From PRO RATA.]
pro·rata·ble adj.
pro·ration n.