What is the average rate of change of the function over the interval x = 0 to x = 9? f(x)=(−2)^x+3

Enter your answer, as a simplified fraction, in the boxes.

Boris needs to buy plastic spoons. brand a has a box 42 spoons for $2.37. brand b has a box of 72 spoons for $3.57. find the unit price for each brand. then state which brand is the better buy based on the unit price. round your answer to the nearest cent.