Bella wants to buy blueberries and raspberries to make a fruit tart. Blueberries cost $3.75 per pound and raspberries cost $2.75 per pound. How much does she spend if she buys 3 pounds of blueberries and 1.5 pounds of raspberries? How much does she spend if she buys xx pounds of blueberries and yy pounds of raspberries?