Please give me an answer with an explanation.

40 and 10

Step-by-step explanation:

1. if the length is 'l' and height is 'h', then according to the condition 1/4*l=h.

2. if the given area is 400, it means, h*l=400;

3. if to substitute h=1/4*l into the formula of the area, then

l*l*1/4=400; ⇔ 1/4*l²=400;

4. if to calculate the value of the 'l', then l=40 (the required length).

5. if to substitute l=40 into 1/4*l=h, then h=10 (the required height).