51. Opcode Decoder

How do you plan to solve it?

module alu_decoder (
    input  [1:0] opcode,
    output reg [3:0] alu_op
);
    always @* begin
        case (opcode)
        2'b00:alu_op=4'b0001;
        2'b01:alu_op=4'b0010;
        2'b10:alu_op=4'b0100;
        2'b11:alu_op=4'b1000;
       default: alu_op=4'b0000;
        endcase
    end
endmodule