Explanation:
Power is the ratio of work to time.
Work is the product of force and displacement.
Work = Force x Displacement
W = F x s
W = 500 x 8 = 4000 J
[tex]\texttt{Power = }\frac{\texttt{Work}}{\texttt{Time}}\\\\\texttt{Power = }\frac{4000}{7.5}\\\\\texttt{Power = }533.33W[/tex]
Power expended by Gerry expend in her running upstairs is 533.33 Hz