What is the average rate of change of ℎ (h) over the interval 5 ≤ t ≤ 9?

a. (h₉ - h₅)/(9 - 5)
b. (h₅ - h₉)/(5 - 9)
c. (h₉ - h₅)/(5 - 9)
d. (h₅ - h₉)/(9 - 5)