Economists have found that the output of a finished product, $f(x, y),$ is sometimes described by the function
$$
f(x, y)=a x^{b} y^{1-b}
$$
where $x$ stands for the amount of money expended on labor, $y$ stands for the amount expended on capital, and $a$ and $b$ are positive constants with $0 < b < 1$
b. Use the result of part (a) to show that if the amount of money expended for labor and capital are both increased by $r \%,$ then the output is also increased by $r \%$