According to B2B, an American survey company, 80% of internet subscribers are not satisfied with their service provider. In order to verify this claim, a randomly selected sample of internet subscribers is surveyed.

a. Assume the company's claim is true and five random subscribers are chosen. Calculate the probability that four or more subscribers are not satisfied with their service, assuming independence.

b. Let's suppose the company's claim is true and 25 internet subscribers are randomly selected. Assuming independence, calculate:

i. The probability that 15 or fewer subscribers in the sample do not have a satisfactory service experience.

ii. The probability that more than 20 subscribers in the sample are dissatisfied with their service. iii. The probability that between 20 and 24 (inclusive) subscribers in the sample are not satisfied with their service.

iv. The probability that exactly 24 subscribers in the sample are dissatisfied with their service.

c. Suppose that we survey 25 randomly selected internet subscribers and find that 15 are not satisfied with their service. Do you believe the company's claim based on a probability you found in this exercise? Please explain.