Tins of the cat food that I buy are normally 80¢ each. They are also available in packs of 6, but there is no advantage to this as they cost $4.80. My neighbour told me this morning that the Everlo supermarket has a special offer this week: 25% off all tins and a further 60¢ off a pack of 6. I have given my son $20 and sent him to Everlo to buy as many tins as he can. How many tins will my son be able to buy with the money I have given him?