Question

Consider this scenario: A traffic signal for eastbound traffic is red for 15 seconds, yellow for 5 seconds,
and green for 30 seconds. The traffic policemen want to know the probability that out of the next x
number of eastbound cars that arrive at that signal(where x>3), 3 of them would be stopped by a red
light.

What is the probability that out of the next 8 eastbound cars that arrive at the signal, exactly 3 will be stopped by a red light?
0.254
0.552
0.806
0.448