Iwill give brainliest to whoever is correct

(2a,a)

Step-by-step explanation:

We know that the longer side (the length) is twice the shorter side (the height). So the x-coordinate will be twice the highest y-coordinate. The highest y-coordinate is a, so the furthest x-coordinate will be 2a. The top right vertex lies on the same y-coordinate as the top left, so the y-coordinate will also be a.

(2a, a) is the answer.

I really hope this helps you =)