Michelle gets a cup of coffee and a muffin every day She pic

Michelle gets a cup of coffee and a muffin every day. She picks a coffee shop at random and independently of her choices on other days. The average price for a cup of coffee is $1.45 with a standard deviation of $.30 and the average price of a muffin is $2.65 with a standard deviation of $.10 and the two prices are independent of each other at each coffee shop.

What is the standard deviation of the amount she spends on breakfast weekly (7 days)?

Solution