Sales data for two years are as follows. Data are aggregated with two months of sales in each

“period.”

MONTHS SALES MONTHS SALES January–February 109 January–February 115 March–April 104 March–April 112 May–June 150 May–June 159 July–August 170 July–August 182 September–October 120 September–October 126 November–December 100 November–December 106

a. Plot the data.

b. Fit a simple linear regression model to the sales data.