1. The problem states that the concentration (Co) is 2 million. 2. To express 2 million in numerical form, recall that 1 million equals 1,000,000. 3. Therefore, 2 million equals $$2 \times 1,000,000 = 2,000,000$$. 4. So, the concentration Co is $$2,000,000$$ in numerical form. This is a straightforward conversion from words to numbers.