$3.90
You have to take $1.16 and multiply it by 2 so that you get the price for 4 pounds then divide 1.16 by 2. Then you have to add together the totals and you'll get the price for 5 pounds.
Or
You could take $1.16 divide it by 2 to get the unit price then multiply (or add it together 5 times) it by 5 to get a total of $3.90