Answer
(a) $60J$
(b) $0J$
(c) $-60J$
Work Step by Step
(a) We can find the required work done as follows:
$W=mgh$
We plug in the known values to obtain:
$W=(3.4)(9.81)(1.8)$
$W=60J$
(b) We know that
$W=mgh$
We plug in the known values to obtain:
$W=(3.4)(9.8)(0)$
$W=0J$
(c) We can find the required in the given scenario as
$W=mg(-h)$
We plug in the known values to obtain:
$W=(3.4)(9.8)(-1.8)$
$W=-60J$