71. Arithmetic Logic Unit

How do you plan to solve it?

/*Write your code here*/
module alu4(input [3:0]a,b,input [2:0]op,output reg [3:0]y,output reg cf);
always@(*)begin
    case(op)
        3'd0 : {cf,y}=a+b;
        3'd1 : {cf,y}=a-b;
        3'd2 : {cf,y}=a&b;
        3'd3 : {cf,y}=a|b;
        3'd4 : {cf,y}=a^b;
        default : {cf,y}=5'd0;
    endcase
end
endmodule