a.) The circuit shown below operates as a 4-bit shift-right register. Suppose that it contains the initial value A[3:0] - 0111. The bits are shown in order of significance, with higher-order bits on the left. A1 Serial Input D Q D Q D Q CLOCK The register's contents are shifted four times to the right. The values applied to the serial input on each of the four shifts are (in the order that they are shifted into the register from first to last) 1-0-1- 0. What are the contents of the shift register following each of the four shifts? 7b.) A ring counter is a shift register that connects the output of the bit that is normally shifted out of the register to the register's serial input. The circuit below implements a normal shift-left operation. Serial Input A1 D Q D Q CLOCK A ring counter would connect the output A3 (the bit that is vacated on each shift-left) to the Serial input that provides a value to A0. A ring counter represents the physical implementation of a circular-shift Suppose that we used this shift register to implement a ring counter. (The shift register does not implement a ring counter by itself, but I just described how to use it to implement one.) If the initial value of this ring counter is 0100, list the sequence of states attained by the ring counter in each of four successive clock cycles