I need help!!

A marketing consultant is hired by a major restaurant chain wishing to investigate the preferences and spending patterns of lunch customers. The CEO of the chain hypothesized that the average customer spends at least $13.50 on lunch. A survey of 25 customers sampled at one of the restaurants found the average lunch bill per customer to be x = $14.50 . Based on previous surveys, the restaurant informs the marketing manager that the standard deviation is o = $3.50. Lunch bills are Normally distributed. To address the CEO's conjecture, the marketing manager carries out a test of hypothesis. The test statistic to use is given by which of the formulas