4. Design logic to add 1 to a 4-bit number, such that sum[3..0]=in(3..01+1. Note that this circuit will be used extensively for counter circuits, which we will study in class soon. Hint: The coding for this function can be understood by noticing that in the binary counting sequence 0000, 0001, 0010, 0011, 0100, 0101, the rightmost bit alternates between 0 and 1, and thus sumO=NOT in O). The next bit sum[1] only changes logical value when in [0] =1. Similarly, sum[2] only changes value when in [0]=1 AND in[1]=1. The logic for the first two bits is given below in Fig.2. Note that the XOR gate is used as a conditional NOT gate