Answer the questions below for the ripple carry 4-bit parallel adder (A+B) and associated timing information shown. a3 a2 a a0 FA cO s2 sl s0 Each full adder is characterized by the following delay times: 2.0 ns for the sum bit and 1.8 ns for the carry-out bit. a) Determine the time required to compute the sum A+B. Note that the sum includes the carry out bit, cO. b) Determine the time required to compute s2