Draw a block diagram for a four-bit counter using one-bit counters. Each one-bit adder is a primitive represented by a box; it has one input a and one output s.
a) Draw the four-bit counter using four one-bit counters.
b) Draw the four-bit counter by first drawing a two-bit counter built from one-bit counters, then using the two-bit counter as a component in the one-bit counter.