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 175 of the subscribers would upgrade to a new cellphone at a reduced cost. Complete parts (a) and (b) below. a. Construct a 95% confidence interval estimate for the population proportion of subscribers that would upgrade to a new cellphone at a reduced cost. (Round to four decimal places as needed.) b. How would the manager in charge of promotional programs use the results in (a)? O A. The manager can infer with 95% confidence that the proportion of subscribers in the sample that would upgrade to a new cellphone at a reduced cost is somewhere in this interval. O B. The manager can infer that the true population proportion of subscribers that would upgrade to a new cellphone at a reduced cost is somewhere in this interval 95% of the time. O C. The manager can infer with 95% confidence that the population proportion of all subscribers that would upgrade to a new cellphone at a reduced cost is somewhere in this interval. O D. The manager can infer that 95% of subscribers that would upgrade to a new cellphone at a reduced cost