(5) Quarterly data for sales of a seasonal product for the four quarters (Winter, Spring, Summer, Fall) of the four years 2016 - 2019 have been analyzed. The sales trend regression equation has a slope of 60 and an intercept of 430. (The first quarter is Winter of 2016). a) [8 points] Compute the trend-based forecast for Spring 2021. Report the forecast value as a whole number. b) [7 points] The seasonal indices for the four quarters are reported in the following table: Quarter Seasonal Index Winter 0.40 Spring 0.20 Summer 0.75 Fall 1.60 Compute the seasonally-adjusted trend forecast for Spring 2021. Report as a whole number by rounding