Computer-assisted learning. Data from a study of computer-ussisted learning by 12 stUdents, showing the total number of responses in completing a lesson (X) und the cost of compuler time (Y. in cents), follow. i: 16 77 2 14 70 3 22 85 4 10 50 5 14 62 6 17 70 7 10 55 8 13 63 9 19 88 10 12 57 11 18 81 12 11 51 a. Fit a linear regression function by ordinary least squares, obtain the residuals, and plot the residuals against X. What does the residual plot suggest'