A cellphone provider has the business objective of wanting to determine 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 sub-scribers would upgrade to a new cellphone at a reduced cost.

a. At the 0.05 level of significance, is there evidence that more than 20% of the customers would upgrade to a new cellphone at a reduced cost?

b. How would the manager in charge of promotional programs concerning residential customers use the results in (a)?