Explanation

(a) 1amu (or 1 u)=$1.6605402\ \times \ 10^{- 27}\ kg$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = \ 1.6\ \times \ 10^{- 24}\ g$
Moreover 1 amu is equivalent to 931 MeV
0r $1.6\ \times \ 10^{- 24}$ g is equivalent to 931 MeV
$\therefore$ 1g is equivalent to $\frac{931}{1.6 \times 10^{- 24}}$ MeV
and $10^{- 3}$ g is equivalent to $\frac{931}{1.6 \times 10^{- 24}} \times 10^{- 3}MeV$
$= \ 5.6\ \times \ 10^{23}\ \ MeV$