Pay and discharge all taxes, assessments and governmental charges or levies imposed upon them, upon their income or profits or upon any properties belonging to them, prior to the date on which penalties attach thereto, and all lawful claims for labor, materials and supplies when due, except that no such tax, assessment, charge, levy or claim need be paid which is being contested in good faith by appropriate proceedings as to which adequate reserves have been established, and no foreclosure, sale or similar proceedings have commenced.