Answer
$P=1046(0.798)^t$
The annual percentage is given by $20.20\%$
Work Step by Step
Let $P=f(x)=a(b)^x $ for the decreasing exponential function as shown in the figure. The value of $a$ can be read directly from the figure as $a= 1046$. We now have $f(x)= 1046(b)^x$. Use the point (5,338) on the graph to find the value of $b$.
$$
\begin{aligned}
f(5) & = 338 \\
1046 b^{5} & =338 \\
b^{5} & =\frac{338}{1046} \\
b & =0.3231^{1 / 5} \\
& =0.798
\end{aligned}
$$ Hence, the global production of CFCs as a function of time since 1989 is given by
$P=1046(0.798)^t$
The annual percentage is given by $r= 1-0.798= 0.202= 20.20\%$.
