An article gave a scatterplot, along with the least-squares line for x = rainfall volume (in cubic meters) and y = runoff volume (in cubic meters), for a particular location. The following data were read from the plot in the paper:
x 8 15 17 20 26 33 43 50 58 70 75 84 99 115 130
y 6 12 15 17 17 27 29 48 40 48 55 72 84 101 102
(a) Calculate the slope and intercept of the least-squares line. (Give the answer to three decimal places.) Intercept 1
Slope 2
(b) Compute an estimate of the average runoff volume when rainfall volume is 75. (Give the answer to two decimal places.)