help me with this question, kindly give a clear answers step and the formula used.

In a Company Cleanex, the manager had conducted a satisfaction survey on his customers from four apartments, which are 30% from apartment A, 15% apartment B, 25% apartment C and the rest for apartment D. However, 5% of apartment A, 6% apartment B, 8% apartment C, and 7% apartment D did not return the questionnaires. a) Draw a probability tree diagram. (3 marks) b ) Find the probability that the customers did not return the survey form. (2 marks) c) Find the probability that a randomly selected customer is from apartment D given that the customers had returned the survey