Biscuit discounts: undo the correct discount first

A shop selling biscuits gave the following offers. A customer who bought a total of 5 or more packets of biscuits was given a discount, regardless of the types of biscuits bought. A 10% discount was given if 5 to 8 packets were bought and a 20% discount if more than 8 packets were bought.

The following table shows the number of packets bought and the total amounts that three customers paid.

Type of biscuits	Mrs Chan	Mr Lim	Mr Tan
Cream	3	5	2
Marie	1	2	1
Almond	3	5	1
Total amount paid in $	10.35	15.72	6.40

Calculate the price per packet for each type of biscuit before the discount.4 marks