Assume monthly contribution to health insurance made by worker is given by function
A(t) = (0:07)t3 - (3:4)t2 + (53:7)t - 240;
where t is number of years after 1980 (like A(1) = monthly contribution in 1981).
a) Determine monthly contribution in 1997?
b) Compute instantaneous rate of change of contributions in 1997?