Jim Bradley Is the Manager of a Bakery, Located on a Major

Jim Bradley is the manager of a bakery, located on a major intersection in a suburban area of Midwestern city. He has been collecting data on sales at his store for the past year. Recently, he has developed a model that he thinks explains sales at the bakery. Unfortunately, he never had a course in statistics, and isn't sure that he has done his regression analysis correctly and asks for your opinion.
According to Jim, weekly sales at the Bradley Bakery can be described by the equation:
Q = 5,000 - 1,000P + 10A + 1.5Y + 400P_c - 25A_c, where Q denotes unit sales, P is the firm's price, A is the firm's advertising spending, Y is the per capita income in the local area, P_c is the average price charged by a nearby competing bakery and A_c is the rival's advertising spending. Jim didn't keep the printout from the analysis. He only kept the equation, which he is eager to use to plan for his likely sales in the next few months. What advice would you give Jim about using the equation?