The grocery store we use does not mark prices on its goods. My wife went to this store, bought four
packages of bacon and five cartons of eggs, and
paid a total of $16.91. Not knowing that she went to
the store, I also went to the same store, purchased
five packages of bacon and four cartons of eggs,
and paid a total of $18.91. Now we want to return four
packages of bacon and four cartons of eggs.
How much will be refunded?