Al and Barb start their new jobs on the same day. Al's schedule is 3 work-days followed by 1 rest-day. Barb's schedule is 7 work-days followed by 3 rest-days. On how many of their first 1000 days do both have rest-days on the same day?<spanclass=′latex−bold′>(A)</span>48<spanclass=′latex−bold′>(B)</span>50<spanclass=′latex−bold′>(C)</span>72<spanclass=′latex−bold′>(D)</span>75<spanclass=′latex−bold′>(E)</span>100