Problems for Section 9.6: Causal Forecasting Models 15. After graduation, you take a position at Top-Slice, a well- known manufacturer of golf balls. One of your duties is to forecast monthly demand for golf balls. Using the follow ing data, you developed a regression model that expresses monthly sales as a function of average temperature for the month Monthly sales = -767.7 + 98.5 (average temperature) MONTHLY AVERAGE SALES TEMPERATURE March 2014 4,670 52 5,310 58 May 6,320 69 June 7,080 75 July 7,210 83 August 7040 82 September 6,590 78 October 5,520 65 November 4640 54 December 4,000 48 January 2015 2,840 41 February 3,170 42 April calculated a. (**) Using Equations (9.8) and (9.9) from the text, show how the a and 6 values of -767.7 and 98.5 were b. (*) Use the regression forecasting model to forecast to- tal golf ball sales for June and July 2015. Average tem- peratures are expected to be 76 degrees in June and 82 degrees in July c. (*) Is this regression model a time series or a causal forecasting model? Explain