Sarah is driving. Her distance in km from Tempe after t hours of driving is given by x = D(t) = 13 + 57t.
a. Determine a formula in terms of x for t = D ^-1 (x).
b. Compute D ^-1 (70).
c. In the expression D ^-1 (x):

What quantity (distance or time) does the x represent?

What quantity (distance or time) does the entire D ^-1 (x) represent?

d. Which of the following statements best describes D ^-1 (x) ?
(1) The ratio of Sarah's distance from Tempe (in km) to x hours of driving.

(2) The reciprocal of Sarah's distance from Tempe (in km) after x hours of driving.

(3) The number of hours of driving needed for Sarah to be x km from Tempe.

(4) Sarah's distance in km from Tempe after x hours of driving.