height or altitude for a parallelogram means the perpendicular distance from one parallel side to the other. Check the picture below.
The answer to this question is d
I think it's another trick question and the answer is 2000.
Well to find the missing side you're going to need the other two. Take the one side and multiply by itself. Take the other one and multiply by itself. Add those two products. Then root it. Basically find something that multiplys by itself to get that product