A family of four went to dinner at a local restaurant. Three of the family members ordered the special dinner that costs $12.88 each and the fourth family member ordered the hamburger and fries combo that costs $6.78. If they want to leave a 15% tip, which of the following expressions represents the amount of tip they should leave?
A. (12.88+6.78)×0.15
B. (3×12.88+6.78)×0.15
C. 3×12.88+6.78
D. [3×(12.88+6.78)]×0.15
