The Figure Below Shows Revenue and Cost Curves of a Natural

The figure below shows revenue and cost curves of a natural monopoly firm. Figure 26.1 In the figure,
D: Demand curve
MR: Marginal revenue curve
MC: Marginal cost curve
ATC: Average total cost curve
According to Figure 26.1, to attain allocative efficiency the regulatory body must attempt to set the price equal to:

A) P₂.
B) P₃.
C) P₁.
D) P₄.
E) P₅.