At what cold-reservoir temperature (in ∘c) would a carnot engine with a hot-reservoir temperature of 420 ∘c have an efficiency of 60 % ?

Tc = 168°C

Explanation:

Carnot engine:

∴ ε: efficiency = 60% = 0.60

∴ Th: hot-reservoir temperature = 420°C

∴ Tc: cold-reservoir temperature = ?

⇒ Tc = (1 - ε)×Th

⇒ Tc = ( 1 - 0.60 )×( 420 °C )

⇒ Tc = 168°C

i believe it is a.) released into

explanation: