Let $f : [0, 1] \rightarrow [0, \infty)$ be continuous. Suppose
$\int_{0}^{x} f(t) \text{d}t \geq f(x)$, for all $x \in [0, 1]$. Then
- No such function exists
- There are infinitely many such functions
- There is only one such function
- There are exactly two such functions