42. Correct. The answer is true. Write S_{t} = S_{0}e^{rt}
in the natural log form: lnS_{t} = lnS_{0 }+ lne^{rt} =
lnS_{0} + rt. Therefore, d(lnS_{t})/dt=
r. In general, the rate of growth of y
= f(x) is defined as r_{y} =[dy/dt]/y = marginal function/total
function = d(lny)/dt.