Answer:
60 %
Explanation:
Efficiency is defined as the ratio of output power to the input power.
Input energy each hour = 9 x 10^12 J
Output energy each hour = 5.4 x 10^12 J
Efficiency = Output energy per hour / input energy per hour
Efficiency = (5.4 x 10^12) / ( 9 x 10^12) = 5.4 / 9 = 0.6
Efficiency in percentage form = 0.6 x 100 = 60 %