> in shortsleep command, the procedure should be ready to process(10usecs)→sleep(20usecs)→after sleep(1000020usecs)→before exit(1000060usecs) > > but what I got from the smaple solution for only shortsleep command is 1000073usecs, is that means exit takes another 10 usecs? And if I try to add another longsleep command like this: > > ..... > > What I got is always 50usecs more than the sample solution, is there any manipulations can be done in different commands at the same time? or is there any manipulations can be done within the sleep time? I'm wondering where I got this 50usecs more? Thanks!