1. **State the problem:** We need to find the upper quartile (Q3), lower quartile (Q1), and then calculate the interquartile range (IQR) from the given cumulative frequency data for discounts. 2. **Understand quartiles:** Quartiles split the data into four equal parts. Since the total frequency is 80 (maximum cumulative frequency), - Lower quartile Q1 corresponds to the 25th percentile (position $=\frac{25}{100} \times 80 = 20$) - Upper quartile Q3 corresponds to the 75th percentile (position $=\frac{75}{100} \times 80 = 60$) 3. **Find Q1:** From the cumulative frequency graph description, - At cumulative frequency 20, the discount is approximately £20. 4. **Find Q3:** At cumulative frequency 60, the discount is approximately £50 (since the curve between 40 to 80 cumulative frequency rises from £40 to £60, the 60th frequency lies near £50). 5. **Calculate the interquartile range:** $$\text{IQR} = Q3 - Q1 = 50 - 20 = 30$$ **Final answers:** - Lower quartile (Q1) = £20 - Upper quartile (Q3) = £50 - Interquartile range (IQR) = £30