Problem 3: A cellphone provider has the business objective of wanting to estimate the proportion

of subscribers who would upgrade to a new cellphone with improved features if it were made

available at a substantially reduced cost. Data are collected from a random sample of 500

subscribers. The results indicate that 135 of the subscribers would upgrade to a new cellphone at

a reduced cost. Construct a 99% confidence interval for the population proportion of subscribers

that would upgrade to a new cellphone at a reduced cost.