Preemptive Priority CPU scheduling Algorithm : <p>Consider a uniprocessor system executing three tasks T1, T2 and T3, each of which is composed of an infinite sequence of jobs (or instances) which arrive periodically at intervals of 3, 7 and 20 milliseconds, respectively. The priority of each task is the inverse of its period and the available tasks are scheduled in order of priority, with the highest priority task scheduled first. Each instance of T1, T2 and T3 requires an execution time of 1, 2 and 4 milliseconds, respectively. Given that all tasks initially arrive at the beginning of the 1st milliseconds and task preemptions are allowed, the first instance of T3 completes its execution at the end of ______________ milliseconds.</p>

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<p><strong>My Take</strong> - I took that beginning of 1st ms means all the process arrives at time = 1 and 0 to 1 time is IDLE. and when I take the gantt chart I get answer as 13, whereas answer = 12 </p>
