$2-$ Given the following demand pattern. Forecast the demand for period $6$ by:

period demand

$\_\_\_\_\_\_\_\_\_\_\_\_\_$

$150$

$240$

$360$

$450$

$560$

$6$

a$)$ The arithmetic average.

b$)$ The weighted moving average where n$=2.$

The weights are $10$ and $5.$

c$)$ Which one of the two is preferable based on the MAD method