Answer:
Tuesday, 13th September
Explanation:
The record date of the share as specified by the MNOP Inc. is fixed on Thursday, 15th September. So the ex-dividend date is on the 14th of September on Wednesday.
Ex dividend date is set by the company on the basis of stock exchange rules. Whether a stock holder will get the dividend or not will depend on the ex dividend date. Generally an ex dividend date is fixed one working day before the date of the record date. In order to get the dividend the buyer have to purchase the stock before the ex dividend date.
Thus in the context, Cheri should buy the stock at least one day before the ex dividend date of the stock that is on 13th September, Tuesday.