A Monopolist Faces a Constant Marginal Cost of $1 Per

A monopolist faces a constant marginal cost of $1 per unit and has no fixed costs. If the price elasticity of demand for this product is constant and equal to -3, then

A) to maximize profits, he should charge a price of $1.50.
B) to maximize profits, he should charge a price of $3.
C) to maximize profits, he should charge a price of $1.33.
D) he is not maximizing profits.
E) None of the above.