Gas in a tank contains a poison at a concentration c_T, but the gas is leaking into the surrounding room at a rate of T cm³/min. Meanwhile, an air conditioner brings fresh air into the room at a rate of A cm³/min. The air in the room is well mixed and leaves through an open window (with the same concentration as in the room). The densities of all the gases are the same. Initially, the concentration of poison in the room (c_R) will rise, but it eventually will reach a steady value. In terms of the given symbols, what is that steady concentration?