Salt water containing 1.92 lb/gal of salt flows at a fixed rate of 2 gal/min into a 100-gal tank, initially filled with fresh water. The density of the incoming solution is 71.8 lb/ft³. The solution, kept uniform by stirring, flows out at a fixed rate of 19.2 lb/min.
a. How many pounds of salt will there be in the tank at the end of 1 h and 40 min?
b. What is the upper limit for the number of pounds of salt in the tank if the process continues indefinitely?
c. How much time will elapse while the quantity of salt in the tank changes from 100 to 150 lb?