Let Yt be the sales during month t (in thousands of dollars) for a photography studio, and let Pt be the price charged for portraits during month t . The data are in the file Week 4 Assignment Chapter...

 LetYt be the sales during montht (in thousands of dollars) for a photography studio, and letPtbe the price charged for portraits during montht. The data are in the file Week 4 Assignment Chapter 12 Problem 64. Use regression to fit the following model to these data:

Yt = a + b1Yt−1 + b2Pt + et

This equation indicates that last month’s sales and the current month’s price are explanatory variables. The last term, et, is an error term.

1. If the price of a portrait during month 21 is $10, what would you predict for sales in month 21?