Katie and Margarita have $20 each to spend at students Choice bookstore where all students receive a 20% discount they both want to purchase a copy of the same book which normally sells for 22.50 plus 10% sales tax to check if she has enough to purchase the book Katie takes 20% of 22.5 and subtract that amount from the normal price she takes 10% of the discount to selling price and add to back to find the purchase amount. Margarita takes 80% of the the normal purchase price and then computes 110% of the reduced price. is Katie correct? is Margarita correct? do they have enough money to purchase the book?