In nuclear reactions,which of the following quantities are conserved?

The correct statement of the following is:

Which of the following elements has the maximum binding energy per nucleon?

The sun radiates energy in all directions. The average radiation received on the earth's surface from the sun is $1.4 \; kW/m^2$. The average earth-sun distance is $1.5 \times 10^{11} \; m$. Calculate the mass lost by the sun per day $(1 \; \text{day} = 86400 \; s)$.

The energy equivalent of $1 \text{ kg}$ of matter is about

Einstein's mass-energy relation emerging out of his famous theory of relativity relates mass $(m)$ to energy $(E)$ as $E = mc^2$,where $c$ is the speed of light in vacuum. At the nuclear level,the magnitudes of energy are very small. The energy at the nuclear level is usually measured in $MeV$,where $1\,MeV = 1.6 \times 10^{-13}\,J$; the masses are measured in unified atomic mass unit $(u)$,where $1\,u = 1.6605 \times 10^{-27}\,kg$.
$(a)$ Show that the energy equivalent of $1\,u$ is approximately $931.5\,MeV$.
$(b)$ $A$ student writes the relation as $1\,u = 931.5\,MeV$. The teacher points out that the relation is dimensionally incorrect. Write the correct relation.