One of policies for reduction of greenhouse gas includes the emission trading. The emissions trading, e.g., cap and trade is a market-based approach, which has been used to control pollutions by providing economic incentives for achieving reductions in the emissions. Recently, in previous work, the efficiency of emission trading has been addressed, and various models have been proposed. In this work, we develop a model for analyzing the decision making of firms' emission reductions by taking into account not only emission trading but also control of the quantity of output. Additionally, we analyze how the output quantity affects the emission reduction cost compared to the existing schemes, and derive the conditions for which the scheme in this work is economically justified.