A major airline operates 350 flights a day throughout the world. The probability that a flight will be delayed for more than one hour, for any reason, is 0.7%. If more than four flights suffer such delays in any one day, the implications for route organization and crewing become serious. Call such a day a ‘flap-day’. Using approximations as appropriate, find the probabilities that

(a) Any particular day is a flap-day;

(b) Two flap-days (not more) occur in one week;

(c) More than fifty flap-days occur in a year of 365 days.