This part deals with Binomial Random Variables. Let p = P(no. of questions guessed correctly]
W = no. of wrong answers
Introduce a "dummy-variable", l, where l = no. of wrong answers out of the (n-k) questions that the student guessed on. In this case, p = 1/5. Plug that into the PMF binomial variable formula, where the parameters are (n-k, l). The expression we get is the distribution of W.
