In a certain town, the mean price of a chocolate chip cookie is $2.30 and the standard deviation is $0.40 at various bakeries. The mean price of a brownie is $3.50 and the standard deviation is $0.20. Ten tourists came to the town together. They separately went to randomly chosen bakeries, and each person bought one item. Each of the seven tourists bought a chocolate chip cookie, and each of the remaining three bought a brownie. If the prices of individual items are independent and normally distributed, what is the probability that the total amount of money the 10 people spent is at most $28 (round off to third decimal place)