Use Figure: Monopoly Profit Maximization

Use Figure: Monopoly Profit Maximization. The figure shows the demand curve, marginal revenue curve, marginal cost curve, and average total cost curve that are faced by a monopolist. At what price level is the marginal revenue of the firm zero?
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Figure: Monopoly Profit Maximization

A) $6
B) $10
C) $11
D) $14