Historical demand for a product is as follows:

                            D E M A N D

April                       60
May                       55
June                      75
July                       60
August                 80
September          75

a .  Using a simple four-month moving average, calculate a forecast for October. 
b .  Using single exponential smoothing with a= 0.2 and a September forecast = 65, calculate 
a forecast for October.

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. 
d .  Calculate a forecast for October.