Total operations = 2+3+4=9
Total no. of concurrent schedules : 9C2 * 7C3 = 1260
1. We need to maintain order of operations of an individual transaction [or it won't be a schedule] in the final interleaved schedule.
2. Out of the 9 possible positions we choose 2 places for T1 and place it operations sequentially , then we choose 3 places for T2 and place its operation sequentially , The remaining 4 places are used for T3 .