Lessee will advise Lessor in writing promptly of (i) any material changes in the coverage or limits provided under any policy required by Section 6.2 of this Agreement and this Exhibit C and (ii) any default in the payment of any premium and of any other act or omission on the part of Lessee which may invalidate or render unenforceable, in whole or in part, any insurance being maintained by Lessee pursuant to this Exhibit C .