c
i.e. \(\frac{2 \mu_{0}}{4 \pi} \frac{ m }{ r ^{2}} \times \frac{7}{ r }=0.4 \times 10^{-4}\)

\(\Rightarrow 2 \times 10^{-7} \times \frac{ m \times 7}{\left(7^{2}+18^{2}\right)^{3 / 2}} \times 10^{4}\)

\(=0.4 \times 10^{-4}\)

\(m =\frac{4 \times 10^{-2} \times(373)^{3 / 2}}{14}\)

\(M = m \times 14 cm = m \times \frac{14}{100}\)

\(=\frac{0.04 \times(373)^{3 / 2}}{14} \times \frac{14}{100}\)

\(=4 \times 10^{-4} \times 7203.82=2.88 J / T\)