4. A certain bacterium grows in culture in a circular region. The radius of the circle, measured in m) = 6 [5/(r2 + 1)} centimetersi is given by 1.Iiihere tis time measured in hours since a circle of a '1cm radius of the bacterium 1was put into the culture. a. Express the area of the bacteria as a function of time. In. Find the exact and approximate area of the bacterial culture in 3 hours. c. Express the circumference of the bacteria as a function of time. d. Find the exact and approximate circumference of the bacteria in 3 hours