What are the key functions of a master schedule? 1. To generate material and capacity requirements 2. To maintain valid priorities 3. An effective capacity utilization 4. Planning the quantity and timing of output over the intermediate time horizons. Select the correct answer using the code given below:

• A. 1, 2 and 3                     
• B. 2, 3 and 4
• C. 1, 3 and 4                     
• D. 1, 2 and 4