We can use the equation:
![age=\text{circumference}+\text{growth rate}](https://img.qammunity.org/2023/formulas/mathematics/high-school/bskbm89ec4jo3ntb0jd19csc6zfiwm7fgj.png)
Age is given as 800
Circumference is 2*pi*r
Growth rate is the rate of change of growth of the tree. We can find this by looking at the linear equation.
The equation is:
y = 4.39x - 6.77
Matching with y = mx + b, we can say:
m = 4.39 [m is the rate of change. So, this is the growth rate]
Now, we substitute into equation to solve for r:
![\begin{gathered} 800=2\pi r+4.39 \\ 800-4.39=2\pi r \\ 795.61=2\pi r \\ r=(795.61)/(2\pi) \\ r=1249.74 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/in1jgpzvv882y5syheokt6643huxf6l5hd.png)
Diameter is double this radius. So,
Diameter = 1249.74 * 2 = 2499.48
Diameter = 2499.48