CREATE TABLE table_71496 ("Lot No." FLOAT, "Diagram" FLOAT, "Mark" TEXT, "Builder" TEXT, "Fleet numbers" TEXT, "Notes" TEXT)

Name the fleet numbers for diagram of 186 and lot number of 30798
SELECT "Fleet numbers" FROM table_71496 WHERE "Diagram" = '186' AND "Lot No." = '30798'
SELECT "Fleet numbers" FROM "table_71496" WHERE "Diagram" = '186' AND "Lot No." = '30798'