Quarterly sales in units for the last two years are as follows: Quarter Year 1 Year 2 I 280 380 II 345 415 III 130 148 IV 215 270 Using linear regression, a straight line was fitted to the sales data. The equation of the fitted line is Y = 210 + 15 t. The first quarter in the data is labeled t = 1. a. Calculate seasonal indexes for this product using the fitted line approach. b. Using the fitted line and seasonal indexes you have just calculated, forecast sales in each quarter of year 3.