PHYSICS! help please?

Question

A carnot engine receives 1000 J from the high temperature reservoir at 500 degrees celsius and does 450 J of work during a cycle. What is the temperature of its low temperature reservoir?

Answer 1

it has efficiency of 450/1000=.45 (45% - work obtained / heat given).

carnot formula: efficiency= (Th-Tl)/Tl = .45 = (737-tl)/737 (in Kelvin!!)

so tl=405K that is 132 degC...