Each of the Borrower and its Subsidiaries will pay or cause to be paid when due all taxes, assessments, governmental charges or levies imposed upon it or its income, profits, payroll or any property belonging to it, including without limitation all withholding taxes, and all claims for labor, materials and supplies which, if unpaid, might become a lien or charge upon any of its properties or assets; provided that Borrower and its Subsidiaries shall not be required to pay any such tax (other than real estate taxes which must be paid regardless of challenge), assessment, charge, levy or claim so long as (a) the validity thereof shall be contested in good faith by appropriate proceedings promptly initiated and diligently conducted by it, and neither execution nor foreclosure sale or similar proceedings shall have been commenced in respect thereof (or such proceedings shall have been stayed pending the disposition of such contest of validity), and it shall have set aside on its books adequate reserves with respect thereto or (b) the nonpayment thereof would not, individually or in the aggregate, reasonably be expected to have a Material Adverse Effect.