Need the PHSTAT Help for this not just the equations

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 price. Data are collected from a random sample of 550 subscribers, and the result indicate that 150 of the subscribers would upgrade to a new cellphone at reduced cost.

State the null and alternative hypotheses.

At 0.05 level of significance, state your decision.

Is there evidence that more that 20% of the customers would upgrade to a new cellphone at a reduced cost?