Answer
$mass = 2.16\times 10^{-8}~kg$
Work Step by Step
We can find the required number of protons:
$\frac{1~C}{1.6\times 10^{-19}~C} = 6.25\times 10^{18}~protons$
We can find the required number of atoms:
$n = \frac{6.25\times 10^{18}}{13} = 4.8\times 10^{17}~atoms$
Note that the atomic mass of aluminum is $26.98~u$
We can find the required mass of aluminum:
$mass = (26.98)(1.67\times 10^{-27}~kg)(4.8\times 10^{17})$
$mass = 2.16\times 10^{-8}~kg$
