An electrical contractor's records during the last five weeks indicate the following 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$.$ Na$$ve$.$

Number of requests for week $6$

b$.$ Four$-$week moving average. $($Round the final answer to$\text{'}2$ decimal places.$)$

Number of requests for week $6$

c$.$ Exponential smoothing with $a=0\mathrm{.}30($Round the intermediate calculations and the final answers to $2$ decimal places.$)$

$\backslash$table$[[F_3,],[F_4,],[F_5,],[F_6,]]$