71. Arithmetic Logic Unit

How do you plan to solve it?

module alu4 (
  input [3:0]a,
  input [3:0]b,
  input [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