4. (20 Points) You have been given the most recent 20 quarters (t) of data on the sales (x) of brand A phones as the following table. You decide to use the multiplicative Holt-Winter method to forecast future sales. Your initial estimates of alpha, beta, and gamma are 0.2, 0.3, and 0.2. However, you lose some data by coincidence. Year 3 5 Quarter 1 2 3 4 1 151 228 2 165 223 269 4 240 383 336 471 433 20 20 a) Luckily, you have processed the data and recorded that y(t) =210, 279, (+2) =2870, 22-2(x1) =8060, ????(xxt) =101315, 222, (x) 2, (x) = 4261270. Assume x = So+Got, what is your estimate of S, and Go? (6 pts) b) What is your estimate of T2]? (4 pts) c) Assume that your calculated average seasonal values are as follows: Tu 0.6489,7121 = as calculated above, T13) = 0.9180, 7(4) = 1.5997, Calculate one- step ahead forecast for the first three quarters. (10 pts) = 4. (20 Points) You have been given the most recent 20 quarters (t) of data on the sales (x) of brand A phones as the following table. You decide to use the multiplicative Holt-Winter method to forecast future sales. Your initial estimates of alpha, beta, and gamma are 0.2, 0.3, and 0.2. However, you lose some data by coincidence. Year 3 5 Quarter 1 2 3 4 1 151 228 2 165 223 269 4 240 383 336 471 433 20 20 a) Luckily, you have processed the data and recorded that y(t) =210, 279, (+2) =2870, 22-2(x1) =8060, ????(xxt) =101315, 222, (x) 2, (x) = 4261270. Assume x = So+Got, what is your estimate of S, and Go? (6 pts) b) What is your estimate of T2]? (4 pts) c) Assume that your calculated average seasonal values are as follows: Tu 0.6489,7121 = as calculated above, T13) = 0.9180, 7(4) = 1.5997, Calculate one- step ahead forecast for the first three quarters. (10 pts) =