Shawn, Rebecca, and Karen went to an office supply store. Shawn bought 6 pencils, 6 markers, and 7 erasers. Her total was $28.50. Rebecca spent $22.25 buying 5 pencils, 4 markers, and 6 erasers. Karen bought 4 pencils, 5 markers, and 5 erasers for $21.25. What is the cost of each item?