Which of the following signs on q and w represent a system that is doing work on the surroundings, as well as losing heat to the surroundings?

a) q = - , w = -
b) q = +, w = +
c) q = -, w = +
d) q = +, w = -
e) none of these represent the system referenced above.

c

Explanation:

In Physics we follow the sign convention i.e. work done by the system is considered as positive i.e. work is being done by system on the surrounding and vice-versa.

For heat :Heat added to the system is considered as Positive while heat loss to surrounding is considered as negative.

thus doing work on the surrounding(work done by system) w=+

Losing heat to the surrounding q=-

b) 10 minutes

girls stopped for 10 minutes.