Customers at your store select their groceries from shelves and then pay. sales records and records of restocks for flaming roast coffee (1 lb size) are as follows:

number of bags tue wed thu fri sat sun mon
sales  5  8  2 19 22 15  3
restock  6 12 12 18 24  0  0
what is the net change in how many bags are on the shelf, from the beginning of tuesday to the end of monday?

(note: a negative number indicates a decrease.)