An electrical contractor's records during the last five weeks indicate the number of job requests:

$\backslash$table$[[$Week$,1,2,3,4,5],[$Requests$,20,22,18,21,22]]$

Predict the number of requests for week $6$ using each of these methods:

a$.$ Naive

b$.$ A four$-$period moving average

c$.$ Exponential smoothing with $=\mathrm{.}30$; use $20$ for week $2$ forecast