2. (2 marks) There are two implementations of a serial adder (A B) as discussed in class. We want to convert them to serial subtractors (A - B). a) (0.5 mark) Using the circuit of Figure 6.5 from the textbook (page 334), show the changes needed to perform A 2's complement of B b) 1.5 marks) Using the circuit of Figure 6.6 from the textbook (page 336), show the changes needed by modifying Table 6.2 (page 335) from an adder to a subtractor circuit