write a vhdl specification for a full adder. And use this full adder component to create a 4-bit ripple-carry (RCA) adder, as shown in figure 2, more specifically how will instantiating the four full adders components to structually model the 4bit rca.

Cin Cin B(0) A(0 B(1) A(1) 4 4-bit Parallel B(2) Adder A(2) B(3) A(3) Figure 2. 4-bit Parallel Adder Sum B FA out Figure 2. Full Adder (FA) FA C1 FA C2 FA C3 FA In In D(0) D(1) D(2) D(3) Cout