Chapter 4 - Polynomials - 4.3 Polynomials - 4.3 Exercise Set - Page 253: 71

2.5 mcg/mL.

To solve this problem, we first draw the vertical line $x=2$. Next, we see where this line intersects the given curve. Finally, from this point, we draw a horizontal line to the y-axis to find the corresponding y value. Doing this, we find that the concentration is about 2.5 mcg/mL.