Final answer:
To determine whether the amount of solvent in the tank is increasing or decreasing at t=4 hours, we need to compare the rate of removal and the rate of pumping at that time.
Step-by-step explanation:
At time t=4 hours, we need to determine whether the amount of solvent in the tank is increasing or decreasing.
The rate at which solvent is being removed from the tank at time t=4 hours can be found by substituting t=4 into the function L(r)=3+10cos(t).
Similarly, the rate at which clean solvent is being pumped into the tank at time t=4 hours can be found by substituting t=4 into the function E(t)=1/2+ln(t^2+4).
If the rate of removal is greater than the rate of pumping, then the amount of solvent in the tank is decreasing. If the rate of removal is less than the rate of pumping, then the amount of solvent in the tank is increasing.
By performing the calculations, we can determine whether the amount of solvent in the tank is increasing or decreasing at time t=4 hours.