SAT Nonlinear functions Question

The function $f(x)=\frac{1}{7}(x-6{)}^2+4$ gives a toy car's height above the ground $f(x)$ , in inches, $x$ seconds after it started moving on an elevated track, where $0\le x\le 10$ . Which of the following is the best interpretation of the vertex of the graph of $y=f(x)$ in the $xy$ -plane?