unless, in the case of clause (i) above, Subcontractor delivers to Contractor another Bond that is valid, binding, and enforceable, and, in the case of clause (ii), Subcontractor delivers to Contractor another Bond issued by a Qualifying Bond Issuer, in each case within seven (7) Business Days of any such event and in each case with such substituted Security and substituted Security Issuer, as the case may be, being subject to the prior written approval of Contractor in its sole and absolute discretion.