please solve by full and half adders

Figures 1 shows a 4-bit unsigned multiplication. Design a 4-bit variable- constant unsigned multiplier where the constant input b = 13. Show all your design steps and draw the logic diagram using the minimum number of components. as a2 at ao aabo albo aobo mb' aobt asb3 asb2 a2b3 aab2 alba aob3 aob2 p, p, Fig. 1 (b) (7marks) Redesign the circuit in (a) using a ROM. Show all your design steps. (4 marks)