Task 4 [30 marks] Make a sequential counter that can loop through composite (i.e. not prime) 4-bit numbers (use ABCD format) at each clock pulse. You should rely on D-flip-flops to represent each bit of a current counter state. Draw state diagram, construct present-next state table, and use K-maps for each bit to acquire functions for all D-flip-flop inputs. When your simplified functions are ready, draw a circuit diagram as implementation of the described counter.