*Please Explain how to do the Linear-trend method not using Excel*

Goodyear Tire and Rubber Company is the ninth largest tire manufacturer in the world. Here are the sales revenues for the past five years: Year 1 2 3 4 5 Revenue (millions) $4,887.9 5,065.4 5,535.6 5,730.8 5,499.7 b. Based on MAD over years 3, 4 and 5, which method (linear-trend or double exponential smoothing method with a = 0.4 and B = 0.2 (start with initial estimates Si = $4,867.90 and T1 = $201.5 for the year 1)) provides the better forecasts? Explain. Forecast the sales revenues for years 6 and 7 based on the better method (20 points)