a. Using a simple four-month moving average, calculate a forecast for October. (Round your answer to 2 decimal places.) b. Using single exponential smoothing with a=0.20 and a September forecast =54, calculate a forecast for October. (Round your answer to 1 decimal places.) c. Using simple linear regression, calculate the trend line for the historical data. Say the X axis is April =1, May =2, and so on, while the Y axis is demand. (Round your intercept value to the nearest whole number and slope value to 2 decimal places.) d. Calculate a forecast for October using your regression formula. (Round your answer to 2 decimal places.)