$3-(25\%)$ The oxygen level in a river can be modelled with the following equation:

$C=10m\frac{g}{L}-20(e^{-(\frac{0\mathrm{.}3}{(km)})x}-e^{-(\frac{0\mathrm{.}85}{(km)})x})m\frac{g}{L}$

Where $C$ is the concentration in $m\frac{g}{L}$ and $x$ is the position in $km$ downstream of a water treatment plant. Use the False Position and Secant method in order to get an approximation of the distance downstream where:

a$.$ The concentration will be below $5m\frac{g}{L}.$

b$.$ The concentration will start to be above $5m\frac{g}{L}$ again.

ii$.$ Find the answer with $2$ significant figures.

iii. Calculate the convergence rate for each iteration and compare the convergence of the two methods. Did you achieve the highest convergence rate?