Statement I
2D = C
2C = B
A+B+C+D+blank = 1600
We dont know anything about the blank block. Insufficient.
Statement II
A = 800
we have no relation of A to B, D or C. Insufficient.
Combining I & II
We dont have any relation between A and B or D or C.
We also dont know about the blank box.
Insufficient.
Hence E.
No rest for the Wicked....