3. In a running race, the times of 80 competitors were recorded. Complete the cumulative frequency table. Draw a cumulative frequency graph of the data. Using the graph estimate the median time. Time t (minutes) Frequency Cumulative frequency 30 < t < 35 7 35 < t < 40 13 40 < t < 45 18 45 < t < 50 25 50 < t < 55 12 55 < t < 60 5