The price of products may increase due to inflation and decrease due to depreciation. derek is studying the change in the price of two products, a and b, over time.

the price f(x), in dollars, of product a after x years is represented by the function below.

f(x) = 72(1.25)x

part a: is the price of product a increasing or decreasing and by what percentage per year? justify your answer.

part b: the table below shows the price f(t), in dollars, of product b after t years:

t (number of years) 1 2 3 4
f(t) (price in dollars) 65 84.5 109.85 142.81

which product recorded a greater percentage change in price over the previous year? justify your answer.