a) What is the timing of the first 8-bit carry select adder (in the notes) built out of 3 4-bit ripple carry adders? b) What is the timing of a 12-bit adder out of 5 4-bit ripple carry adders? c) What is the timing of the best 64-bit carry-select adder you can build out of a single-size of ripple carry adder? How big are the adders? How many are there?