A Reuters article reports, "The newest item appearing on the Fed's balance sheet was loans it has taken on from banks participating in the Small Business Administration's "Payroll Protection Program," initially rolled out at $349 billion but set to be expanded under new appropriations from Congress after the original amount ran out in less than two weeks. The Fed held just over $8 billion of PPP loans as of Wednesday, an amount certain to rise in the coming weeks." Please explain the rationale (if there is any) for this policy