A Carnot engine, having an efficiency of `eta=1//10` as heat engine, is used as a refrigerator. If the work done on the system is 10J, the amount of energy absorbed from the reservoir at lower temperature is

Explanation

Coefficient of performance of refrigerator
`beta=(1-eta)/(eta)=(1-1//10)/(1//10)=9=("Heat extracted")/("workdone")`
`therefore` Heat extracted `=9xx10=90J`