Which of the following is required for a buy-sell agreement to establish the estate tax value of closely-held stock subject to the agreement?

A. The agreement must provide for the purchase of additional insurance as the value of the stock increases.

B. The stock certificates must bear a legend stating their sale is subject to restrictions and where the restrictions can be found.

C. The agreement must explain how and when the purchased stock will be delivered.

D. The estate must be obligated to sell the stock at a price that is determinable by a reasonable formula or a method contained in the agreement.