$\begin{array}{1 1}11.8J\\12.8J\\10.8J\\13.8J\end{array} $

Answer : 11.8J

To lift a 3kg object at constant speed,an upward force equal in magnitude to its weight,$mg=(3)(9.8N)$,must be exerted on the object.

The work done by this force is what we refer to as the work done against gravity :

Work against gravity = $mgh$

$\qquad\qquad\qquad\quad=[(3)(9.8)N](0.40m)$

$\qquad\qquad\qquad\quad=11.8J$

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