Concept: The question tests on the basics of Mensuration.
Solution:
Let the dimensions of the concrete block be l, b, h for length, breadth and height respectively.
The volume of a cube = l.b.h
St(1):- Please let us know as and when you have queries in future.
The lateral faces are the four sides of the block.(You can imagine the four "walls" of a room)
Given, l h =200 and b h=200
=> l h=b h
=> l = b
However we do not know the third side to determine the value of the volume. (Insufficient)
St(2):- The top of the block is square and has an area of 400 square inches.
Let the dimension of the top square face be a units.
=> a^2 = 400
=> a = 20
Even though two of the dimensions are 20 each, we still do not know the third dimension needed for the volume.(Insufficient)
On combining both:-
l = b
l h = 200 and hence 20 * h =200 (20 is obtained as data from the second statement. You can also use b h=20)
Hence volume = lbh = 20*20*10 (Sufficient) option(C)