Mark Gershon, owner of a musical instrument dis-tributorship, thinks that demand for guitars may be related to the number of television appearances by the popular group Maroon 5 during the previous month. Mark has collected the data shown in the following table-

a) Graph these data to see whether a linear equation might describe the relationship between the group's television shows and guitar sales.

b) Use the least- squares regression method to derive a forecasting equation.

c) What is your estimate for guitar sales if Maroon 5 performed on TV nine times last month?

d) What are the correlation coefficient ( r) and the coefficient of determination ( r2) for this model, and what do they mean?