From the given data, the amount of energy required to break the nucleus of aluminium ${}_{13}{}^{27}\mathrm{Al}$ is __________$x\times {10}^{-3} \mathrm{J}$. 

Mass of neutron $=1.00866 \mathrm{u}$
Mass of proton $=1.00726 \mathrm{u}$
Mass of Aluminium nucleus $=27.18846 \mathrm{u}$
(Assume $1 \mathrm{u}$ corresponds to $x \mathrm{J}$ of energy)
(Round off to the nearest integer)

If $f$ denotes the ratio of the number of nuclei decayed $\left(N_d\right)$ to the number of nuclei at $t=0, \left(N_0\right)$ then for a collection of radioactive nuclei, the rate of change of $f$ with respect to time is given as:

 $[\lambda$ is the radioactive decay constant]

Consider the following statements:
$A$. Atoms of each element emit characteristics spectrum.
$B.$ According to Bohr's Postulate, an electron in a hydrogen atom revolves in a certain stationary orbit.

$C.$ The density of nuclear matter depends on the size of the nucleus.
$D.$ A free neutron is stable but a free proton decay is possible.
$E.$ Radioactivity is an indication of the instability of nuclei. Choose the correct answer from the options given below.