Answer:
1. (c) 18 J
2. 70%
Explanation:
1. Thermal energy released (waste) = input energy (it is usually more) - output (usually less_used to perform useful work)
= 60 joules - 42 joules
= 18 joules
2. % energy efficiency = output/input x 100%
= (42/60) x 100%
= 70%
I hope this helps. have a nice studies
