It takes a large pump 30 hours to empty a swimming pool and it takes a smaller pump 75 hours to empty the same pool how much time will it take to empty the pool using both pumps

The line plot below represents the number of letters written to overseas pen pals by the students at the waverly middle school.each x represents 10 students. how many students wrote more than 6 and fewer than 20 letters. a.250 b.240 c.230 d.220