At the price оf $5 per pаck оf bаtteries, Durаcell sells 10,000 packs оf batteries and Energizer sells 15,000 packs of batteries. When the price rises to $7.50, Duracell sells 12,000 packs of batteries and Energizer sells 17,000 packs of batteries. What is the market supply at $7.50?