A regression has been performed on two continuous centered predictors x and z. It is known that n = 116, sd(x) = 1.73, and sd(z) = 2.01. The estimated regression line is

Yi = 28.63 + 7.15xi + 2.82zi − 1.12xizi

Compute the simple slope for the regression of Y on x when z is one standard deviation

below mean.

a. 1.5

b. 4.9

c. 9.4

d. 38.0