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, level 2, and level 3.

1 iflevel 2 1 if level3 x2_0 otherwise x3-10 otherwise y = 48.8-3.4x1 + .07x_ 2.4x2-75x3 + 3.7x1x2