1. Jack buys small tins of tomatoes every week. They usually cost 50¢ each. Last week,
however, Jack saw that the shop was selling six large tins of tomatoes plus a bag of
pasta for $7.50. He worked out that the pasta was normally $2. Jack decided that he
could use one large tin of tomatoes instead of two small tins so he bought 18 large tins
of tomatoes together with three bags of pasta.
This week, however, the small tins of tomatoes are on offer at $1.60 for a pack of four.
How much more did Jack pay last week for tinned tomatoes than if he had bought them
this week?
Answer is in what unit?