Logic gates

Here is the half-adder plus full-adder that adds two-bit numbers. Interpret AB as one two-bit number, and CD as another. The sum of them should be the value of the three-bit number XTS. That is, for the inputs ABCD = “1011”, that means AB = 10₂ = 2₁₀ and CD = 11₂ = 3₁₀. Add these numbers to get 5₁₀ = 101₂. Thus, your outputs XTS should be 101.