Draw it as though your working on a board like this. Include the logic gates you use like ANDs/ORs/etc, and the connections the wires have between the parts.

Implement 1-bit full adder using decoder. The inputs for 1-bit full adder are A, B and Cin . The outputs for the 1-bit full adder are Sum and Cout . A decoder can implement more than one function at a same time, in this question, your circuit should provide both the outputs using single decoder.

+5V a BI