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 + 1);
    3'b010: {cf, y} = {1'b0, a & b};
    3'b011: {cf, y} = {1'b0, a | b};
    3'b100: {cf, y} = {1'b0, a ^ b};
    default: {cf, y} = 5'd0;
    endcase
end

endmodule