CREATE TABLE table_49718 ("Year" FLOAT, "U.S." TEXT, "U.S. R&B" TEXT, "U.S. Rap" TEXT, "Album" TEXT)

What is the U.S. rap rank for the song with a U.S. R&B 23 rank?
SELECT "U.S. Rap" FROM table_49718 WHERE "U.S. R&B" = '23'
SELECT "U.S. Rap" FROM "table_49718" WHERE "U.S. R&B" = '23'