Efficiency = \(\frac{ poweroutput}{powerinput}\)

but power output = \(\frac{ f \times s}{ t}\) = \(\frac{75 \times 10 \times 3}{ 30}\) = 75W

Efficiency = 80%, power output = 75w

then 0.8 =  \(\frac{ 75}{powerinput}\)

power input =  \(\frac{ 75}{0.8}\) = 93.75W.