ABC bookstore sells one customer 10 used books and 5 new books for $150. Another customer buys 15 used books and 1 new book for $108. How much
is one used book (u), and one new book (n)?
A. u = $18, n = $6
B. u= $10, n = $5
c. u = $6, n = $18
D. u = $15, n = $1