48. Tilman's Resource Model Suppose that the rate of growth of a plant in a certain habitat depends on a single resource-for instance, nitrogen. Assume that the growth rate \( f(R) \) depends on the resource level \( R \) in accordance with the formula
\[
f(R)=a \frac{R}{k+R}
\]
where \( a \) and \( k \) are constants. Express the percentage error of the growth rate, \( 100 \frac{\Delta f}{f} \), as a function of the percentage error of the resource level, \( 100 \frac{\Delta R}{k} \).
