CREATE TABLE table_18599 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

what was the number of candidates when Leon Sacks was incumbent?
SELECT COUNT("Candidates") FROM table_18599 WHERE "Incumbent" = 'Leon Sacks'
SELECT COUNT("Candidates") FROM "table_18599" WHERE "Incumbent" = 'Leon Sacks'