(Bloomberg) -- A bipartisan group of four US senators wants the Internal Revenue Service and Treasury Department to investigate whether nonprofit hospitals are abusing their tax-exempt status. Most Read from BloombergRetirees Face $17,400 Cut to Social Security Benefits in 2033First American City to Tame Inflation Owes Its Success to Affordable HousingEcuador Presidential Candidate Assassinated, Suspect Shot DeadEveryone Wants to Work at UPS After Teamsters DealNaira Extends Drop From Record as