The monthly sales for Yazici$$ Batteries, Inc., were as$$ follows:

$$

Month

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sept

Oct

Nov

Dec

Sales

$20$

$20$

$16$

$14$

$15$

$18$

$15$

$17$

$19$

$22$

$20$

$23$

This exercise contains only parts b and c$.$