1. The problem is to find the difference in cost between 300 g of potatoes and 300 g of carrots using the graph. 2. From the graph description, the cost of 500 g of potatoes is just below 30 p, approximately 29 p, so the rate for potatoes is about $\frac{29}{500}$ p per gram. 3. The cost of 500 g of carrots is 20 p, so the rate for carrots is $\frac{20}{500}$ p per gram. 4. Calculate the cost for 300 g of potatoes: $$300 \times \frac{29}{500} = \frac{8700}{500} = 17.4 \text{ p}$$ 5. Calculate the cost for 300 g of carrots: $$300 \times \frac{20}{500} = \frac{6000}{500} = 12 \text{ p}$$ 6. Find the difference in cost: $$17.4 - 12 = 5.4 \text{ p}$$ Final answer: The difference between the cost of 300 g of potatoes and 300 g of carrots is 5.4 p.