By which process is the energy released from the Sun?

The phenomenon in which a proton flips is

The energy released in the fusion of $2 \ kg$ of hydrogen deep in the sun is $E_{H}$ and the energy released in the fission of $2 \ kg$ of ${ }^{235} U$ is $E_U$. The ratio $\frac{E_H}{E_U}$ is approximately :
(Consider the fusion reaction as $4{ }_1^1 H + 2 e^{-} \rightarrow { }_2^4 He + 2 \nu + 6 \gamma + 26.7 \ MeV$,energy released in the fission reaction of ${ }^{235} U$ is $200 \ MeV$ per fission nucleus and $N_{A} = 6.023 \times 10^{23}$ )

Explain an example in which heat transfer is necessary.

$A$ nuclear fuel rod generates energy at a rate of $5 \times 10^8 \,W/m^3$. It is in the shape of a cylinder of radius $4.0 \,mm$ and length $0.20 \,m$. $A$ coolant of specific heat $4 \times 10^3 \,J \cdot kg^{-1} \cdot K^{-1}$ flows past it at a rate of $0.2 \,kg/s$. The temperature rise in this coolant is approximately ............ $^{\circ}C$.

$A$ certain mass of Hydrogen is changed to Helium by the process of fusion. The mass defect in the fusion reaction is $0.02866 \, u$. The energy liberated per $u$ is ........... $MeV$. (Given $1 \, u = 931 \, MeV$)