Data Sufficiency

we're given the total area = 1600 acres..
In statement 1 we're given the relationship between C,B, and D.. no information about A and the blank area . Eliminate A and D

In statement 2 we're given the Area of A = 800 acres, no information about C,B, and D.. eliminate B

combining them..

Here is my question, which is :

we know that the total area = 1600 and the area of A =800, so 800 acers left for C,B,D, and the blank area..
C= 2D, B= 2C ..

Since C= 2D then Could we conclude that the blank area equals D ??? why not ??