#### Answer

(a) W = -5.25 J
(b) W = 0

#### Work Step by Step

(a) We can find the work done by the tension.
$W = F\cdot d$
$W = F ~d~cos(\theta)$
$W = (15~N)(0.35~m)~cos(180^{\circ})$
$W = (15~N)(0.35~m)(-1)$
$W = -5.25~J$
(b) We can find the work done by gravity.
$W = F\cdot d$
$W = F ~d~cos(\theta)$
$W = F~d~cos(90^{\circ})$
$W = F~d~(0)$
$W = 0$