Answer from cs61c-cg (Daniel Lau 16776873) for Question 4
select=0 in0=x in1=x out=x expected=x time=0

it is because the time is not incremented manually, a, b and expected value will be fluctuating between 1 and 0. hence when the time frame is at 0, there will be undefined value. Another variable f is not defined above, hence it is an undefine value x.