Answer
a) $C_n=1.1C_{n-1}$
b) $\approx8.6~g/L$
Work Step by Step
a) If the original amount was $4$ and it increases by $10\%$ each day, then $C_n=1.1C_{n-1}$ and $C_n=4(1.1)^{n}$.
b) Plugging in $n=8$ into the formula, we get:
$C_8=4(1.1)^{8}\approx8.6~g/L$
