4.4 Extend the SRC instruction set by adding the xor command, (op- 19), which is similar to the and command, but performs the XOR operation instead of AND a. Develop the abstract RTN for the xor command. b. Write the concrete RTN and control signals for the xor instruction for the 1-bus SRC microarchitecture. (Unfortunately, the SRC ALU does not have the XOR operation as one of its primitives, but only the operations ADD, SUB, AND, OR, SHR, SHL, NEG, NOT, C B, and INC4.)