Correct choice is (a) 38 frames
For explanation I would say: If the system creates 250 frames per second, or 1/4 frames per millisecond, then G = ¼.
S = G × e−2G = 0.152 (15.2 percent).
This means that
Throughput = 250 × 0.152 = 38.
Only 38 frames out of 250 will probably survive.