(i)[2]
State three conditions that have to be met for a situation to be modelled by a binomial distribution.
(ii)[3]
George is planning to invest part of his monthly salary. He places a fixed amount of this into an investment each month for 18 months. In any month, the probability that he buys shares in a large company is $0.25$, the probability that he buys shares in a small company is $0.15$, and the probability that he invests in a savings account is $0.6$. Find the probability that George will buy shares in a small company in at least $3$ of these $18$ months.