for a physical fitness test, scores are determined by the expression 2ps - 45m, where p and s are the numbers of push-ups and sit-ups an athlete can do in one minute for each activity, and m is the number of minutes the athlete takes to run a mile. during the test, abraham did 21 push-ups and 30 sit-ups and ran the mile in 10 minutes. javed got the same score, but did 4 more push-ups and ran the mile in 12 minutes. how many sit-ups did javed do in one minute?