The problem says "above adder" and there is no "above adder" in the quesion. The problem should gives delays of
gates: AND, OR and XOR
and also of CARRY and SUM.
Only one should be given, but not both.
Given fact that we are dealing with carry look ahead adder and given gate delays, we are supposed to find sum and carry delays. It makes no sense to also give carry and sum delays itself in the question.
Also the given carry and sum delays seems to be un-achievable with given gate delays.
Also it says "The sum and carry output of full adder takes 20ns and 10ns respectively.", but here we are dealing with look ahead adder. Standalone full adder carry - sum delays does makes sense here.
Can someone explain how this fact "The sum and carry output of full adder takes 20ns and 10ns respectively" can be used?