Start by getting what a 1% depression would be:
267,000 / 100 = 2,670 (this is 1%)
In September, his cost increases 2%:
267,000 + 2 * 2,670 = 272,340
In October, the cost decreased by 8%:
267,000 - 8 * 2,670 = 245640
Add the three months up:
267,000 + 272,340 + 245,640 = $784,980