Aheat engine operating between energy reservoirs at 20? c and 650 ? c has 26 % of the maximum possible efficiency.

 The maximum possible efficiency, i.e the efficiency of a Carnot engine , is give by the ratio of the absolute temperatures of hot and cold reservoir. 
η_max = 1 - (T_c/T_h) 

For this engine: 
η_max = 1 - [ (20 +273)K/(600 + 273)K ] = 0.66 = 66% 

The actual efficiency of the engine is 30%, i.e. 
η = 0.3 ∙ 0.664 = 0.20 = 20 % 

On the other hand thermal efficiency is defined as the ratio of work done to the amount of heat absorbed from hot reservoir: 
η = W/Q_h 

So the heat required from hot reservoir is: 
Q_h = W/η = 1000J / 0.20 = 5000J

Julia would be observing a. static electricity was caused by her sweater rubbing against her shirt and transferring electrons. she didn't touch anything metal, so that would cancel out b.she most likely didn't rub her sweater against her hair either, so that cancels out c.she also didn't scoot across the carpet while trying to take her sweater off, that cancels out d.so that leaves a.a. is correct.