Math Help Please?

p(>= 40 times) =
1 - p(< 40 times) =
1 - p(0, 1, 2, 3, or 4 quarters work first 39 times) =
1 - (p(0 in 39 times) + p(1 in 39 times) + p(2 in 39 times) + p(3 in 39 times) + p(4 in 39 times)) =
1 - (39C0 + 39C1 + 39C2 + 39C3 + 39C4)