a. Given that Xi, Yi and Ci represent the addend bits and carry-in at position i, i.e. Stage i, specify and compare the logical expressions for Si and Ci+1, i.e. the sum and carry-out from Stage i, between the one-bit half adder, the one-bit full adder, and the onebit carry look-ahead (CLA) adder.
b. What is the worst-case delay of an n-bit ripple-carry adder built with 2-input gates? Justify your answer. (Hint: Look at the full adder gate implementation.)