i. Show the truth table of a 74LS139 which is a 2 x 4 IC decoder. (1 mark) Given the truth table of a combinational circuit that accepts three input bits: minuend (X), subtrahend (Y) and previous borrow (Bp) and produce two output bits: difference (D) and borrow next (BN). Implement the Boolean function for D and By using 74LS138 IC and external 74XX series logic gates. (3 marks) Y B, D 0 0 0 0 0 0 0 1 1 1 0 1 0 1 1 0 1 1 1 0 1 0 0 0 1 1 0 1 0 0 1 1 0 0 0 1 1 1 1