$4\mathrm{.}55$ The following multiple regression model was developed to predict job performance as

measured by a company job performance evaluation index based on a preemployment test

score and college grade point average $($GPA$)$:

hat$(y)=35+20x_1+50x_2$

Where

hat$(y)=$ job performance evaluation index

$x_1=$ preemployment test score

$x_2=$ college GPA

a$.$ Forecast the job performance index for an applicant who had a $3\mathrm{.}0$ GPA and scored $80$ on the

preemployment test.

b$.$ Forecast the job performance index for an applicant who had a $2\mathrm{.}5$ GPA and scored $70$ on the

preemployment test.