A 12.0 cm object is 9.0 cm from a convex mirror that has a focal length of -4.5 cm. What is the distance of the image from the mirror?

A) –3 cm
B) –4 cm
C) 3 cm
D) 4 cm

The answer to this question is C.

 (a) the work done on the gas

From the definition of work in thermodynamics,

W = integral (PdV)

It is said that the process above is done at constant volume. Therefore, the value of dV is zero which would result to 

W = integral (PdV) = 0

(b) the increase in internal energy of the gas
 From the first law of thermodynamics,

ΔU = Q + W

where U is the change in internal energy, Q is the heat and W is the work which is zero in this case

ΔU = Q = 209 J

(c) its final temperature
at constant volume,
Q = nCv(T2 - T1)
209 = 1 (3R/2) (T2 - 300)
T = 316.76 K