Question 1184079


b.)  The differential equation is 

{{{dQ/dt = 0.32 - Q/125}}}, 


where Q is the amount of salt in the solution in kg, after time t.


The solution to this D.E. is {{{Q(t) = 40 + 40*e^(-t/125)}}}.   After 4.5 hours, or t = 270 minutes,
{{{Q(270) = 40 + 40*e^(-270/125) = red(44.613)}}} kg.