A capacitor, $C_1=5\mathrm{.}0F,$ is charged up to $8$ V $.$ It is then connected to a second uncharged capacitor, $C_2=2\mathrm{.}5F.$ The voltage across the capacitor $C_1$ after the system has come to equilibrium is

$4\mathrm{.}0$ V $.$

$8\mathrm{.}0$ V $.$

$12\mathrm{.}0$ V $.$

$2\mathrm{.}67$ V $.$

$5\mathrm{.}33$ V $.$