Chapter 13 - Partial Derivatives - 13.1 Functions Of Two Or More Variables - Exercises Set 13.1 - Page 914: 9

(a) $\quad C(25,3)=5\left(e^{-0.6}-e^{-3}\right)=2.50 \mathrm{mg} / \mathrm{L}$ (b) $C(100, t)=20\left(e^{-0.2 t}-e^{-t}\right)$ (c) $C(x, 1)=0.2 x\left(e^{-0.2}-e^{-1}\right)$

Plugging in the given points: (a) $\quad C(25,3)=5\left(e^{-0.6}-e^{-3}\right)=2.50 \mathrm{mg} / \mathrm{L}$ (b) $C(100, t)=20\left(e^{-0.2 t}-e^{-t}\right)$ (c) $C(x, 1)=0.2 x\left(e^{-0.2}-e^{-1}\right)$