Determine whether the following statements are true and give an explanation or counterexample.

a. A quantity that increases at 6%/yr obeys the growth function y(t) = y0e^0.06t.

b. If a quantity increases by 10%/yr, it increases by 30% over 3 years.

c. A quantity decreases by one-third every month. Therefore, it decreases exponentially.

d. If the rate constant of an exponential growth function is increased, its doubling time is decreased.

e. If a quantity increases exponentially, the time required to increase by a factor of 10 remains constant for all time.