Six crosses on a grid with dark gridlines split into halves: one at 0 minutes with a cumulative frequency of 0, then 5 at 10 minutes, 19 at 20, 40 at 30, 52 at 40 and 60 at 60. The time axis runs from 0 to 60 minutes and the cumulative frequency axis from 0 to 60, both by 5. No curve is drawn, so students join the points with a smooth curve.