A local tire dealer wants to predict the number of tires sold each month. He believes that the number of tires sold is a linear function of the amount of money invested in advertising. He randomly selects 6 months of data consisting of tire sales (in thousands of tires) and advertising expenditures (in thousands of dollars). Based on the data set with 6 observations, the simple linear regression equation of the least squares line is = 3 + 1 x.= 24= 124= 42= 338= 196 MSE = 4

Required:
Using the sums of the squares given above, determine the 90% confidence interval for the mean value of monthly tire sales when the advertising expenditure is $5000.

a. (3.32 12.68)
b. (3.74 12.26)
c. (6.62 9.38)
d. (6.08 9.92)