Question 107
Determine whether there exists a function $f$ defined on the set of all positive real numbers and taking positive values such that
$$
f(x + y) \geq y f(x) + f(f(x))
$$
for all positive $x$ and $y$.
$$
f(x + y) \geq y f(x) + f(f(x))
$$
for all positive $x$ and $y$.