When Three-Frame Differencing (TFD) is applied in real time, it performs an AND operation on two pictures, one is the difference picture between I(t) and I(t-N), and the other is the difference picture between I(t-N) and I(t-2N). a. Write the pseudo-code of the TFD algorithm without using SFD(N). b. Write the pseudo-code the TFD algorithm with using SFD(N).