Ans: A
Let $x\text{ kg}$ be the mean weight of the actresses. Then we have
$\begin{array}{rcl}
\dfrac{60 \times 63 +40 \times x}{60+40} & = & 57 \\
3780 +40x & = & 5700 \\
x & = & 48
\end{array}$
Therefore, the mean weight of the actresses is $48\text{ kg}$.
