20. Raw materials inventory on January 1, 2021 totaled $10,000, while ending inventory on January 31, 2021 totaled $15,000. Purchases of raw materials during the month of January totaled $25,000. Direct labor incurred in January totaled $18,000, and manufacturing overhead applied in January totaled $12,000. (a.) Calculate the cost of materials available for use in January. (b.) Calculate the cost of materials used in production during January. (c.) Calculate the total cost of goods manufactured during January