WASHINGTON (AP) — President Barack Obama will make a formal announcement Monday welcoming the weekend agreement by the pharmaceutical industry to help close a gap in prescription drug coverage under Medicare. The president has invited Barry Rand, head of the senior citizens’ advocacy group AARP, to appear with him. The drug companies have pledged to spend $80 billion over the next decade to help reduce the cost of drugs for seniors and pay for a portion of Obama’s health care legislation. The deal was struck with Sen. Max Baucus, the chairman of the Senate Finance Committee, as well as the White House.