At the supermarket, limes are sold for $5.00 per bag and grapefruits for $12.50 per box. A bag contains 6 limes and a box contains 15 grapefruits. Only a whole number of bags and a whole number of boxes can be purchased. Part A: On Thursday, a chef purchased 12 bags of limes and some boxes of grapefruits. If the total cost was $135.00, how many boxes of grapefruits were purchased? Part B: On Sundays only, there is a 20% discount on the price of a bag of limes and a 15% discount on the price of a box of grapefruits. What is the total cost for 4 bags of limes and 8 boxes of grapefruits? Part C: On Tuesday, the chef needed 80 limes and 50 grapefruits. The chef purchased just enough bags and boxes. Determine how much the purchase cost her. Part D: On Wednesday, the chef made tarts that each required 1 lime and 2 grapefruits. If the chef spent exactly $75 total on limes and grapefruit, determine the greatest number of tarts she could have made?