65. Ripple Carry Adder

How do you plan to solve it?

// 1-bit Full Adder (to be used by the 4-bit RCA)
module full_adder_1bit (
    input  a, b, cin,
    output sum, cout
);
   assign sum=a^b^cin;
   assign cout=(a&b)|(b&cin)|(a&cin);
endmodule

// 4-bit Ripple Carry Adder – chain 4 full adders
module rca4_chain (
    input  [3:0] a,
    input  [3:0] b,
    input        cin,
    output [3:0] sum,
    output       cout
);
   wire c1,c2,c3;
   full_adder_1bit f1(a[0],b[0],cin,sum[0],c1);
   full_adder_1bit f2(a[1],b[1],c1,sum[1],c2);
   full_adder_1bit f3(a[2],b[2],c2,sum[2],c3);
   full_adder_1bit f4(a[3],b[3],c3,sum[3],cout);


endmodule