Which of the following statements is true when a company has a production bottleneck?

a$.$ The product with the highest unit contribution margin per production bottleneck hour should be emphasized in the market.

b$.$ The theory of constraints is used as a manufacturing strategy.

c$.$ The company should attempt to maximize its profits, subject to the production bottleneck.

d$.$ The product with the lowest unit contribution margin per production bottleneck hour is the most profitable product per bottleneck hour.