Hi
p(willing to work overtime without pay) = .6, n = 15
a) Mean = .6*15 = 9, sd = √9 = 3
b) P(x ≥ 13) = 1 - binomcdf(15, .6, 12) = .0271
c) P(x=10) = 15C10(.6)^10(.4)^4 0r binompdf(15, .6, 10)= .1859
Single x-value
p and q are the probabilities of success and failure respectively.
In this case p = .6 & q = .4