1. 75% of the passengers buy in-flight meal in a flight from Hong Kong to Singapore. The flight is full and there are twelve passengers. What is the probability that

(a) (i) eight passengers in a cabin buys the in-flight meal;

(ii) more than 11 passengers in a cabin buys the in-flight meal  

(iii) less than three passengers in a cabin buys the in-flight meal  

(b) Find the mean number of passengers in a cabin do not buy the in-flight meal.