The standard quantity that is produces is multiplied to the standard price. The product is subtracted to the quantity variance and will be divided to the standard price. The product you have acquired will be the units that are produced.
4,500 pounds x $2.50 = 11,250
11,250 - $375 = 10,875
10,875 / $2.50 = 4,350
Answer: There are 4,350 units produced.