Gabriel wants to buy some items in a hardware store. The cost of 3 handles and 1 bolt is £11. The cost of 2 handles and 3 bolts is £12. The cost of 7 handles and 5 bolts is £31. Work out how much the following cost: a) 10 handles and 6 bolts. b) 5 handles and 2 bolts. c) 12 handles and 9 bolts.