could you please help me with this question and explain why

Andy is a restaurant owner. He believes 84% of his customers are satisfied with the food quality of his restaurant. From a random sample of 87 customers, what are the following probabilities? (Bound to 2 decimal places for all z-values and round all other answers to 4 decimal places, if needed.) (a) What is the probability that less than 74 customers are satisfied with the food quality? :| (b) What is the probability that at least 74 customers are satisfied with the food quality? :1 (c) What is the probability that the sample proportion of customers who are satisfied with the food quality is between 82% and 89%? :1