Q3 : A- If the CPU scheduling policy is priority preemptive, draw gantt chart and calculate the average waiting time. (Higher number represents higher priority) B- Explain why the following statement is false:When several threads access shared information in main memory, mutual exclusion must be enforced to prevent the production of indeterminate results. C- Explain how the disabling and enabling of interrupts is useful in implementing mutual exclusion primitives on uniprocessor systems