Dilbert forgot to study for the multiple-choice exam.

Dilbert forgot to review for the multiple-choice examination. Every query has 4 decisions and there are 50 questions. Dilbert, in his infinite knowledge, decides to randomly guess on every downside. Discover the chance for every:

x~bin(50,0.25)
P(x) = 50Cx *0.25^x *0.75^(50-x)
a. P(30 <= x <= 50) = 1.642286e-7
b. P(20 <= x <= 29) = 0.01391744
c. P(10 <= x <= 19) = 0.8223985
d. P(0 <= x<= 9) = 0.1636839