Part A: At the school, 75 band members need to raise a total of $8,250 for a trip. So far, they have raised $3,120. How much money, in dollars, per band member, still needs to be raised for the trip? Part B: The entire band decides to have a concert to raise the money for the trip. Tickets for the concert will cost $7.50 each. A local business agrees to donate an additional $0.50 for each $1.00 in ticket sales to the band for their trip. What is the least number of concert tickets the band must sell in order to raise the rest of the money needed for the trip?