#### Answer

418 degrees Celsius

#### Work Step by Step

We know that 140 Joules of work is done, for this is the change in energy. Thus, we find the efficiency:
$= \frac{140}{240}=.583$
Thus, it follows:
$ T_h=\frac{T_c}{1-.583} = \frac{288K}{1-.583} \approx 691 K \approx 418 ^{\circ}C$