$3\mathrm{.}6$: $$P$3\mathrm{.}6$ Imagine that you have placed a limit order to buy $100$ shares of Herr Mining Co$.$ at a price of $$68,$ although the stock is currently selling for $$71.$ Discuss the consequences, if any, of each of the following situations.

a$.$ The stock price drops to $$69$ per share two months before cancellation of the limit$$order$.$

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b$.$ The stock gradually drops to $$65.$

c$.$ The minimum stock price achieved before cancellation of the limit order was $$68\mathrm{.}50.$ When the limit order was canceled, the stock was selling for $$77\mathrm{.}50$per share.