A grocery store's receipts show that Sunday customer purchases have a skewed distribution with a mean of $31 and standard deviation of $21. Suppose the store had 311 customers this Sunday. a) Estimate the probability that the store's revenues were at least $10,000. b) If, on a typical Sunday, the store serves 311 customers, how much does the store take in on the worst 1% of such days? a) The probability is (Round to four decimal places as needed.) b) The store takes in at most $ (Round to two decimal places as needed.)