On August 6, A&B Construction has three outstanding invoices payable to Excel Builder’s Supply. Invoice 535, dated July 16, is for $3228.56; Invoice 598, dated July 24, is for $2945.31; and Invoice 678, dated August 3, is for $6217.69. All invoices have terms 4/10, 2/20, n/60. If A&B makes a $10,000 payment to Excel on August 6, what further payment on August 15 will settle the account? Note that Excel applies payments to the oldest invoices first.