Answer
$4.0\times10^9C$
Work Step by Step
First find out how many moles of water there are in 75 kg, multiply by the number of atoms per mole and then by the number of protons in a water molecule to find the total number of protons. Then, multiply by the charge per proton.
$$Q=(75kg)\frac{6.022\times10^{23}water\; molecules}{0.018kg}\frac{10 protons}{molecule}\frac{1.602\times10^{-19}C}{proton}$$
$$=4.0\times10^9C$$
