Puzzle - Rate
Yesterday my mother asked me to buy some stamps. Stamps, in the land of BrainBashers, are available in 2p, 7p, 10p, 15p and 20p denominations. For three types of stamp I was asked to buy five of each. For the other two types of stamp, I was asked to buy six of each. Unfortunately I forgot which I was supposed to buy five of and which to buy six of. Luckily my mother had given me the exact money required to buy the stamps, £3.00 and the shopkeeper was able to give me the correct stamps. Which stamps did I buy?
[Ref: ZOKI] © Kevin Stone