A 1900 L tank contains 950 L of water with a salt concentration of 8 g/L. Water with a salt concentration of 50 g/L flows into the tank at a rate of 75 L/min. The fluid mixes instantaneously, and is pumped out at a specified rate R_out. Let y(t) denote the quantity of salt in the tank at time t. Assume R_out = 65 L/min. What is the salt concentration when the tank overflows?