71. Arithmetic Logic Unit

How do you plan to solve it?

/*Write your code here*/
module alu4(
    input wire[3:0] a,b,
    input wire [2:0] op,
    output reg [3:0] y,
    output reg cf
);
always @* begin 
    case(op)
    3'b000:{cf,y}=a+b;
    3'b001:{cf,y}=a-b;
    3'b010:begin 
        y=a&b;
        cf=0;
    end
    3'b011:begin 
        y=a|b;
        cf=0;
    end
    3'b100:begin 
        y=a^b;
        cf=0;
    end
    default:begin 
        y=4'b0000;
        cf=0;
    end
    endcase
end
endmodule