CREATE TABLE table_18540 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

What is the number of candidates for pennsylvania 3
SELECT COUNT("Candidates") FROM table_18540 WHERE "District" = 'Pennsylvania 3'
SELECT COUNT("Candidates") FROM "table_18540" WHERE "District" = 'Pennsylvania 3'