8.8 X is a continuous variable that takes on values between 5 and 100. Z is a binary variable. Sketch the following regression functions (with values of X between 5 and 100 on the horizontal axis and values of Y n on the vertical axis):

a. Y n

= 2.0 + 3.0 * ln(X).

b. Y n

= 2.0 - 3.0 * ln(X).

c. i. Y n

= 2.0 + 3.0 * ln(X) + 4.0Z, with Z = 1.

ii. Same as (i), but with Z = 0.

d. i. Y n

= 2.0 + 3.0 * ln(X) + 4.0Z - 1.0 * Z * ln(X), with Z = 1.

ii. Same as (i), but with Z = 0.

e. Y n

= 1.0 + 125.0X - 0.01X2.