The mass equivalent of 931 MeV energy is

$1.66 \times 10^{-27} \mathrm{~kg}$ $6.02 \times 10^{-24} \mathrm{~kg}$ $1.66 \times 10^{-20} \mathrm{~kg}$ $6.02 \times 10^{-27} \mathrm{~kg}$

$1.66 \times 10^{-27} \mathrm{~kg}$

$m=\frac{E}{c^2}=\frac{931 \times 1.6 \times 10^{-13}}{\left(3 \times 10^8\right)^2}=1.66 \times 10^{-27} \mathrm{~kg}$