If an electron and a positron annihilate,the energy released is ........

Let ${m_p}$ be the mass of a proton,${m_n}$ the mass of a neutron,${M_1}$ the mass of a $_{10}^{20}Ne$ nucleus,and ${M_2}$ the mass of a $_{20}^{40}Ca$ nucleus. Then:

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A:$ The binding energy per nucleon is practically independent of the atomic number for nuclei of mass number in the range $30$ to $170$.
Reason $R:$ Nuclear force is short-ranged.
In the light of the above statements, choose the correct answer from the options given below:

Degenerate electron pressure will not be sufficient to prevent the core collapse of a white dwarf if its mass becomes $n$ times the solar mass. The value of $n$ is:

Write the equation of mass-energy equivalence.

If the binding energy per nucleon in $_3^7Li$ and $_2^4He$ nuclei are $5.60 \, MeV$ and $7.06 \, MeV$ respectively,then in the reaction $p + {}_3^7Li \to 2 {}_2^4He$,the energy of the proton must be ........... $MeV$.