Demand for a certain product is forecast to be 800 units per month, averaged over all 12 months of the year. The product follows a seasonal pattern, for which the January monthly index is 0.8. What is the seasonally-adjusted sales forecast for January?

(A) 798.75 units
(B) 640 units
(C) 83.33 units
(D) 801.25 units
(E) 1000 units