$[$QX$]$: $4-21$ The following data give the starting salary for students who

recently graduated from a local university and accepted jobs soon after

graduation. The starting salary, grade$-$point average $($GPA$),$ and major

$($business or other$)$ are provided.

a$.$ Using a computer, develop a regression model that could be used to

predict starting salary based on GPA and major.

b$.$ Use this model to predict the starting salary for a business major with

a GPA of $3\mathrm{.}0.$

c$.$ What does the model say about the starting salary for a business

major compared to a nonbusiness major?

d$.$ Do you believe this model is useful in predicting the starting salary?

Justify your answer, using information provided in the computer

output.