Centerville Bikes and Stuff (CBS) sells motorcycles and accessories. The number of helmets sold by CBS per week for the past six weeks follows. 2 3 4 5 6 Week 1 Value 19 12 15 10 18 13 Using the naive method (most recent value) as the forecast for the next week, compute the following measures of forecast accuracy. (a) mean absolute error MAE= (b) mean squared error MSE- (c) mean absolute percentage error (Round your answer to two decimal places.) MAPE % (d) What is the forecast for week 7?