Consider the model:

where x1 is a quantitative variable and

The resulting least squares prediction equation is

a. What is the equation of the response curve for E(y) when x2 = 0 and x3 = 0? When x2 = 1 and x3 = 0? When x2 = 0 and x3 = 1?
b. On the same graph, plot the least squares prediction equation associated with level 1, with level 2, and with level 3.

I if level 2 0 otherwise 1 if level 3 0 otherwise = 48.8-3.4x + .07x _ 2.4x275x3 +