Answer
$Work = 7.48\times 10^{-11}~J$
Work Step by Step
In part (b), we found that the initial stored energy is $U_i = 4.52\times 10^{-11}~J$
In part (c), we found that the final stored energy is $U_f = 1.20\times 10^{-10}~J$
We can find the work required to separate the plates:
$Work = \Delta U$
$Work = U_f- U_i$
$Work = (1.20\times 10^{-10}~J)- (4.52\times 10^{-11}~J)$
$Work = (12.0\times 10^{-11}~J)- (4.52\times 10^{-11}~J)$
$Work = 7.48\times 10^{-11}~J$
