In each cycle of its operation, a heat engine expels 3,900 J of energy and performs 1,900 J of mechanical work. (a) How much thermal energy must be added to the engine in each cycle

the area between the graph and the t axis

reserve is the answer

the total distance that martina travels that day is

(distance from home to mom's office) plus (distance from mom's office to school)

plus (distance from school to library) plus (distance from library to friend's house)

plus (distance from friend's house to martina's house).

(we don't know what any of these distance actually is.)

what is the actual question though?