how to find the mean

The mean amount purchased by each customer at Churchill's Grocery Store is $30 with a standard deviation of $8. The population is positively skewed. For a sample of 53 customers, answer the following questions: a. What is the likelihood the sample mean is at least $33? (Round the z-value to 2 decimal places and the final answer to 4 decimal places.) Sample mean b. What is the likelihood the sample mean is greater than $28 but less than $33? (Round the z-value to 2 decimal places and the final answer to 4 decimal places.) Sample mean c. Within what limits will 95% of the sample means occur? (Round the final answers to 2 decimal places.) Sample mean and