In a study designed to predict blood cholesterol levels from amount of daily saturated fat in grams (X1) and number of hours of daily exercise (X2), we determine that the slope of X1 is 5, the slope of X2 is -4, and the y intercept is 130. Which of the following formulas is the regression equation for these data?
Select one:
a. ? = 130 + 5(X1) -4(X2)
b. ? = 130 + 5(X1) + 4(X2)
c. ? = 130 + 1(X)
d. ? = 130 -5(X1) -4(X2)