Mark and Elisa each improved their yards by planting daylilies and ornamental grass. They bought their supplies from the same store. Mark spent $120 on 6 daylilies and 6 bunches of ornamental grass. Elisa spent $231 on 12 daylilies and 11 bunches of ornamental grass. Find the cost of one daylily and the cost of one bunch of ornamental grass.