Input data
Mary purchased
4 tires
$ 63.10 per tire
$ 5.20 per tire shipping
$ 7.76 per tire for mounting
Mary's total for the 4 tires with mounting and balancing would be $340 plus 8% sales tax.
Procedure
Total in mail

Total in local store

The difference between the two forms of purchasing is

Mary saved a total of $62.96