Answer
$$
102 M_{s}
$$
Work Step by Step
From $$F_{\text {grav }}=G M m / r^{2}=m v^{2} / r $$
$\text { we find } M \infty v^{2}$
$ \text { Thus, the mass of Sun would be } $
$$
M_{s}^{\prime}=\left(\frac{v_{\text {Mercury }}}{v_{\text {Pluto }}}\right)^{2} M_{s}=\left(\frac{47.9 \mathrm{km} / \mathrm{s}}{4.74 \mathrm{km} / \mathrm{s}}\right)^{2} M_{s}=102 M_{s}
$$
