h = 3a + 28.6

A pediatrician uses the model above to estimate the height h of a boy, in inches, in terms of the boy’s age a , in years, between the ages of 2 and 5. Based on the model, what estimated increase, in inches, of a boy’s height each year ?

A) 3

B) 5.7

C) 9.5

D) 14.3