A bookstore charges a standard rate for paperback or hardback books. The cost of a paperback book is 4 dollars less than the cost of a hardback book. Recently, one day of sales totaled $1065.10. That day the bookstore sold 51 paperback books and 47 hardback books. Write a system representing this situation. Use the graph to estimate the solution of the system. What does the solution mean in this situation? How much does each type of book cost? Use substitution to verify your solution.