Over a long period, total phosphorus (TP) has been discharged to a lake through sewage and surface water runoff at a rate of 10 tons/day. Measures were then taken to reduce the TP load to 1 ton/day. Assume that TP decays by a first order process with a rate constant of 0.001 days^-1. The volume of the lake is 380x10^8 m^3 with a steady-flow in and out of 500 cms (cubic meters per second). What is the TP concentration in the lake one week after the change in loading has occurred.