A $\backslash (240-\backslash$mathrm$\{$V$\}\backslash )$ shunt motor takes a current of $3\mathrm{.}5$ A on no load. The armature circuit resistance is $0\mathrm{.}5$ n and the shunt$-$field$-$winding resistance is $160$ n $.$ When the motor oper$-$ates at full load at $2400$ rpm $,$ it takes $24$ A $.$ Determine $($a$)$ its efficiency at full load, $($b$)$ torque developed and the useful torque, $($c$)$ the no$-$load speed, and $($d$)$ percent speed regulation. Sketch the powerflow diagram for each operating condition.