Context:  The Giants' home opener was played on Monday night and they took a 28-16 victory over the NFC West runners-up from the previous year. The Rams, coached by former Giants defensive coordinator Steve Spagnuolo, took an early lead on a Josh Brown field goal, but that would be their only lead as Eli Manning hit Hakeem Nicks and Domenik Hixon for touchdowns. A Michael Boley fumble return added to that and gave New York a 21-6 lead at the half. St. Louis' only touchdown came in the third quarter as Bradford found Alexander to cut the Giants' lead to 28-16, where the game finished. Manning finished with 200 yards passing and threw his first two touchdown passes of the season while Bradford threw for 331 and one score. After the game, it was announced that Hixon would be lost for the year with a torn ACL.

Question: How many points did the Giants lead by at halftime?

Answer:
15