Answer:
their actions will likely lead to a(n) INCREASE in the price of good XYZ on Monday through Thursday and a(n) DECREASE in the price of good XYZ on Friday.
Explanation:
As the speculator will purchase to sale it on weekend; the demand for this days will icnrease up to a point at which the price increase above 50.
On Fridays as the supply will start to grow sooner or later the consumers will fill their needs fullfil and purchase only if the price is lower than 65.
In the long-run thus, the speculators actions will stabiize the goods price through the week