A $3-$phase. $400V,50Hz$ induction motor takes a power input of $70$ KW at its full$-$load speed of $1440$ rpm $.$ The total stator losses are $2$ KW and the friction and windage losses are $3$ KW $.$ Calculate :

$($i$)$ slip and slip speed

$(8)$

$($ii$)$ rotor ohmic loss

$($iii$)$ shaft power

$($iv$)$ shaft torque and

$($v$)$ efficiency.