Identify which of the following sentences describes the working of the heat engine. An automobile engine is a real-world example of the concept of a heat engine, which the diagram illustrates. It receives heat from a high-temperature system, converts some of the heat into work, and loses the rest of the heat to a low-temperature system. When such a machine works in cycles, it can continuously use a source of heat to do work.

There is a sweet potato with an initial uniform temperature of 25 c and it has an average diameter of 70 mm. thermal conductivity and diffusivity of the potato are 0.62 w/m c and 0.2 x 10^-6 m^2/s. respectively. it is to be cooled by refrigerated air at 1.8°c flowing at a velocity of 4 m/s. the average heat transfer coefficient between the potato and the air is 25 w/m2·°c. determine how long it will take for the center temperature of the potato to drop to 5.5°c