2022 Cayley Problem 6

Yihana walks for 10 minutes. A graph of her elevation in metres versus time in minutes is shown. The length of time for which she was walking uphill is

\textbf{(A)}\ 5\ \text{minutes}\quad \textbf{(B)}\ 6\ \text{minutes}\quad \textbf{(C)}\ 4\ \text{minutes}\quad \textbf{(D)}\ 7\ \text{minutes}\quad \textbf{(E)}\ 8\ \text{minutes}

If there are no answer choices shown, enter a numerical answer.

Full credit to this problem is given to the CEMC, you may view all Cayley contests here.