Find a function E(t) that models the operator's efficiency.

The rate of change of a machine operator's efficiency, E'(t) = 30 -10t + ,given as a percentage per hour (not a decimal), t hours after starting work is given by . After one hour working, it is known that the operator's efficiency is 70%. Find a function E(t) that models the operator's efficiency. . E(t)=[A]_(5pts)