Exercise N 4: (14 points) A full 1-bit additional presents below, it has three inputs (a, b, and sin the carry incoming), and two outputs (the sum bit s and the outgoing carry bit cout). A B Cin- -S -Cout 1- Propose a VHDL code for the 1-bit additional circuit (4 points) 2- Use component above to design a 4-bit adder and propose a the VHDL code (6 points) 4- Propose a VHDL Testbench code for the 4-bit adder (4 points)