Gina pumps 40 cubic inches of air per second into a balloon. the function below shows the total amount of air f(t) inside the balloon after t seconds. f(w) = 40t + 5 which statement best describes the y-intercept of the graph of the function?

For this case, the first thing you should know is that the intersection with the y-axis occurs when the time equals zero.
 Mathematically we have:
 For t = 0:
 f (0) = 40 (0) + 5
 f (0) = 0 + 5
 f (0) = 5
 
 The intersection with the y-axis represents the total amount of initial air before starting to pump air.
 The initial air quantity is: 
 5 in ^ 3