There are four free blocks of sizes 4k, 8k 20k, 2k
Request No. - J1, J2, J3, J4, J5, J6, J7
Allocate block – 2K, 20K, 4K, 6K, 8K, 20K, 10K
Usage time - 4, 10, 2, 8, 4, 1, 8
it will wait to free block used by J2. So it will wait for 10 unit time, then J6 will complete in 1 unit time. So total time 11 unit is taken to process request of J7 and J7 takes unit time to complete the request.
Total time taken by J7 = 10 + 1 + 8 = 19 unit time