U.S. candidate Biden ramps up spending on Facebook ads

U.S. presidential candidate Joe Biden more than tripled his weekly spending on Facebook advertising in the run-up to Tuesday's nomination contests, another sign the former vice president is ramping up his campaign.Biden became the Democratic contest's frontrunner last week when he won "Super Tuesday" contests in 10 states, overtaking U.S. Senator Bernie Sanders of Vermont in the delegate count for their party's nomination.The winner of the Democratic nomination will challenge Republican Presiden