Answer:
work done he has done is equal to 6452.712 J
Step-by-step explanation:
given, 
Assume the mass of the cheerleader be equal to 70.8 kg
she is lift up off to the height of 0.31 m 
acceleration due to gravity = 9.8 m/s² 
number of time she was lift = N = 30 times
 work done = N W 
W = m g h 
 work done = N m g h 
 work done = 30 x 70.8 x 9.8 x 0.31
 = 6452.712 J 
hence, work done he has done is equal to 6452.712 J