CREATE TABLE table_28928 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" TEXT, "Result" TEXT, "Candidates" TEXT)

How many incumbents are there in Pennsylvania 5?
SELECT COUNT("Incumbent") FROM table_28928 WHERE "District" = 'Pennsylvania 5'
SELECT COUNT("Incumbent") FROM "table_28928" WHERE "District" = 'Pennsylvania 5'