In a p$+-$n Si junction, the n side has a donor concentration of $10163.$ If $=10103,$ relative dielectric constant $=12,$ calculate the depletion width at a reverse bias of $100$ V$?$ What is the electric field at the mid$-$point of the depletion region on the n side? $($Hint: Remember that p$+$ means very heavily doped!$)$