Olivia is in business. She takes old tires and chops them up for use in playgrounds under the swings. Her business functions best when its ability to produce chopped up tire bits is exactly match to the supply of old used tires available. Olivia's business output starts at 15,000 square feet of material produced and increases 3,000 square feet each month. Her supply of old tires starts out at a level of 10,000 square feet and increases 4,000 square feet each month. In how many months will Olivia's business be functioning optimally?