A store is selling two mixtures of coffee beans in one pound bags. The first mixture has 12 ounces of Sumatra combined with 4 ounces of Celebes kalossi, and cost $42. The second mixtures has 4 ounces of Sumatra and 12 ounces of Celebes kalossi, and costs $30. How much does one ounce of Celebes Kalossi cost ?