Find the equation for instantaneous acceleration for each of the following distance-time functions d(t)= 0.5t2 - 0.1t+3

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