A colony of bacteria is estimated to have a population of P(t) = (10t^2+6)/(t^3+3) million ...

 A colony of bacteria is estimated to have a population of P(t) = (10t^2+6)/(t^3+3) million t hours after the introduction of a toxin designed to kill the bacteria.
a. What is the population at the time the toxin is introduced?
b. At what time is the population of the bacteria colony the greatest and what is that population?
c. At what time is the bacteria population decreasing at a rate of approximately 300,000 bacteria per hour?