QA QB QC QD D D D 0 D HCK Ck Ck CK k Figure 2 Figure 2 shows the logic circuit for a sequential circuit where QD is the most significant bit. i) Write down the Boolean expressions for DA, DB, DC, and DD. (8 marks) ii) Write down the state table. (20 marks) iii) Write down the state diagram. (12 marks) iv) What is the function of this sequential circuit? (10 marks)