(a) Draw a 4-bit ALU designed from the unlabeled 1-bit ALU shown below (the same one as in Problem 1). Label all the input and output signals on your diagran.. ALUO (b) Assume that a[3:0] = 3, b[3:0] = 7 and that subtraction function is desired, where: a-b=3-7= -4. Write down the control signals in the table below. Operation Subtraction Ainvert Binvert CarryIn for ALUO Operation (binary only) (c) What is the result in binary? What does this number represent? Explain fully. (d) On your 4-bit ALU diagram in part (a), label all inputs and outputs with the values in part (b). In other words: a3 = 0, a2 = 0, a1 = 1, a0 = 1, etc.