Solve the problem. 12) The concentration of a certain drug in the bloodstream t minutes after swallowing a pill containing the drug can be approximated using the equation C(t) = _(3t + 1) -1/2, where C(t) is the concentration in arbitrary units and t is in minutes. Find the rate of change of concentration with respect to time att = 5 minutes. Find an equation for the line tangent to the given curve at the indicated point. 13) y4 + x3 = y2 + 11x at (0, 1) Solve the problem. Round your answer, if appropriate. 14) A ladder is slipping down a vertical wall. If the ladder is 20 ft long and the top of it is slipping at the constant rate of 4 ft/s, how fast is the bottom of the ladder moving along t ground when the bottom is 16 ft from the wall? 15) A spherical balloon is inflated with helium at a rate of 110n ft3/min. How fast is the balloon's radius increasing when the radius is 5 ft? 16) A spherical balloon has sprung a leak. When the radius is 1 cm, the radius is changing at rate of - - cm/s. Find the rate of change of the volume at this time. Solve the problem. 17) Suppose that the amount in grams of a radioactive substance present at time t (in years) is given by A(t) = 890e-0.73t. Find the rate of change of the qu