$A$ series combination of $n_1$ capacitors,each of value $C_1$,is charged by a source of potential difference $4V$. When another parallel combination of $n_2$ capacitors,each of value $C_2$,is charged by a source of potential difference $V$,it has the same total energy stored in it as the first combination has. The value of $C_2$ in terms of $C_1$ is:

• A
  $\frac{2C_1}{n_1n_2}$
• B
  $16 \frac{n_2}{n_1} C_1$
• C
  $2 \frac{n_2}{n_1} C_1$
• D
  $\frac{16C_1}{n_1n_2}$