$8.$ A d$.$e$.$ series motor on full load takes $50$ A from $230$ V d$.$e$.$ mains while the speed wa $900$ r$.$p$.$m$.$ The armature and field resistances of the motor are $0\mathrm{.}22$ and $0\mathrm{.}022,$ respective The total voltage drop due to the brush contact is $2$ V$.$ The iron and friction losses togeth amount to $5\%$ of the input in full$-$load condition. $($a$)$ Calculate the power delivered by motor shaft. $($b$)$ If an additional load torque of $10$ N$-$m is put on the shaft, what is the m speed? Assume the losses remain the same as in full load condition.