A 0 to 6 counter consist of 3 flip-flops and a combination circuit of 2 input gate(s). The combination circuit consists of

In the circuit shown in Figure, A is a parallel in, parallel-out 4-bit register, which loads at the rising edge of the clock C. The input lines are connected to a 4-bit bus, W. Its output acts as the input to a 16×4 ROM whose output is floating when the enable input E is 0. A partial table of the contents of the ROM is as follows

The clock to the register is shown, and the data on the W bus at time t$$_1$$ is 0110. The data on the bus at time t$$_2$$ is

With out any additional circuitry, an 8:1 MUX can be used to obtain

The number of distinct Boolean expressions of 4 variables is