1. **Stating the problem:** You have an API cost of 0.2 per call and you add another 0.2 to make a profit, so the selling price per call is 0.4. 2. **Formula used:** Profit per call = Selling price per call - Cost price per call 3. **Calculate profit per call:** $$\text{Profit per call} = 0.4 - 0.2 = 0.2$$ 4. **Calculate total profit if someone buys 1000 worth of API calls:** First, find how many calls are bought for 1000: $$\text{Number of calls} = \frac{1000}{0.4}$$ 5. **Simplify the number of calls:** $$\text{Number of calls} = \cancel{\frac{1000}{0.4}} = 2500$$ 6. **Calculate total profit:** $$\text{Total profit} = \text{Profit per call} \times \text{Number of calls} = 0.2 \times 2500 = 500$$ **Final answer:** Your profit from 1000 worth of API calls sold at 0.4 each with a cost of 0.2 is 500.