Now, with a bill delegating how to spend nearly $4 billion in American Rescue Plan Act and state surplus funding sitting on his desk, Baker must put his signature on it quickly. He received the legislation Dec. 3 after it languished for months amid House and Senate deliberations and he has until Monday to act. It contains a desperately needed $964 million in health-care relief, according to a Massachusetts Taxpayers Foundation analysis. That’s the single largest expenditure within the bill.