An Inventor Tries to Sell You His New Heat Engine $40 \mathrm {~J}$

Short Answer

An inventor tries to sell you his new heat engine that takes in $40 \mathrm {~J}$ of heat at $87 ^ { \circ } \mathrm { C }$ on each cycle, expels $30 \mathrm {~J}$ at $27 ^ { \circ } \mathrm { C }$ , and does $10 \mathrm {~J}$ of work. Would it be wise to invest in this engine? Back up your conclusion with numerical calculations.