Consider the following four (A–D) closed thermodynamic systems at an instant. The systems consist of a single-phase substance.

Answer the questions posed for the following scenarios:

A. At a particular instant, energy enters a system as a heat interaction at a rate of 14 kJ/s. No energy leaves. Is the rate  change of the system energy positive, negative, or zero? Give the numerical value. Is the system temperature increasing, decreasing, or constant? Explain your answers. 

B. At a particular instant, energy exits a system as a work interaction at a rate of 7 kJ/s. No energy enters. Is the rate of change of the system energy positive, negative, or zero? Give the numerical value. Is the system temperature increasing, decreasing, or constant? Explain your answers.

C. At an instant, energy enters a system as a heat interaction at a rate of 20 kJ/s and energy exits the system as a work interaction at a rate of 15 kJ/s. Is the rate of change of the system energy positive, negative, or zero? Give the numerical value. Is the system temperature increasing, decreasing, or constant? Explain your answers.

D. At an instant, energy enters a system as a heat interaction at a rate of 16 kJ/s, and energy exits the system as a work interaction at a rate of 30 kJ/s. Is the rate of change of the system energy positive, negative, or zero? Give the numerical value. Is the system temperature increasing, decreasing, or constant? Explain your answers.