10 J of heat and 5 J of work are supplied to the system, what

10 J of heat and 5 J of work are supplied to the system, what is the change in internal energy?
A. 5 J
B. 10 J
C. 15 J
D. 20 J
Correct choice is C. 15 J

For explanation: ∆U = 5 + 10 = 15 J.