F = focal lenght = 67.1 cm
u= distance between mirror and object = 16.76 cm
1/f = 1/v + 1/u
1/67.1 = -1/16.76 + 1/u
1/67.1 + 1/16.76 = 1/u
u = 13.41
Answer:
U1 = U2 since the temperature inside the balloon does not change
Q1 - W1 = Q2 - W2
Work done by the balloon = W2 - W1 (on the environment)
W2 - W1 = Q2 - Q1 = 75 J heat put into balloon
So the balloon does 75 J on the environment