This added to optimism after Fed Chair Jerome Powell said on Wednesday it was time to slow down coming interest rate hikes, while also signaling a protracted economic adjustment amid high borrowing costs. Costco Wholesale Corp COST.O fell 3.2% after the membership-only retail chain reported slower sales growth in November. By Ankika Biswas and Shreyashi Sanyal Dec 1 (Reuters) - Wall Street was set to extend gains on Thursday after data showed a mild easing in inflation and solid consumer spending in October, adding to hopes of a likely downshift in the Federal Reserve's policy on aggressive rate hikes.