Table 1.21 shows the concentration, $c,$ of creatinine in the bloodstream of a dog. $^{41}$
(a) Including units, find the average rate at which the concentration is changing between the
(i) $6^{\mathrm{th}}$ and $8^{\mathrm{th}}$ minutes. (ii) $\quad 8^{\mathrm{th}}$ and $10^{\mathrm{th}}$ minutes.
(b) Explain the sign and relative magnitudes of your results in terms of creatinine.
$$\begin{array}{c|ccccc}
\hline t \text { (minutes) } & 2 & 4 & 6 & 8 & 10 \\
\hline c(\mathrm{mg} / \mathrm{ml}) & 0.439 & 0.383 & 0.336 & 0.298 & 0.266 \\
\hline
\end{array}$$