The value V of an item t years after it is purchased is V = 9000e^-0.6t for 0 ≤ t ≤ 5.

(a) Use a graphing utility to graph the function.

(b) Find the rates of change of V with respect to t when t = 1 and t = 4.

(c) Use a graphing utility to graph the tangent lines to the
function when t = 1 and t = 4.