CREATE TABLE table_16155 ("Model" FLOAT, "Introduction" CLOB, "Discontinued" CLOB, "CPU Speed" CLOB, "Print resolution  ( DPI )  Resolution is given in dots per inch  ( DPI ) " CLOB, "Print speed  ( PPM ) " CLOB, "Standard memory" CLOB, "Maximum memory" CLOB)

What is the model number introduced May 1999?
SELECT MAX("Model") FROM table_16155 WHERE "Introduction" = 'May 1999'
SELECT MAX("Model") FROM "table_16155" WHERE "Introduction" = 'May 1999'