5 bookmarks are $23 + $9.30(bonus) = $32.30. Take total amount of money($304.50) divide by the amount per set ($32.30) = 9.42724... This means that there are 9 groups of 5 bookmarks... So you take 9x5=45... After using a total of $290.70, there is still $13.80 left. Take total amount left ($13.80) divide by the amount per set ($4.60)=3. There are 3 groups of 1 bookmark. Therefore, 45 + 3 =48 bookmarks.