1. The problem states the constraint on the variable $x$ as $0 \leq x \leq h$. 2. This means $x$ can take any value starting from 0 up to and including $h$. 3. This is a domain restriction often used in problems involving intervals, such as integration limits, piecewise functions, or physical constraints. 4. The notation $0 \leq x \leq h$ means $x$ is greater than or equal to 0 and less than or equal to $h$. 5. This defines a closed interval on the real number line from 0 to $h$. 6. If $h$ is a positive number, this interval includes all numbers between 0 and $h$. 7. If $h$ is zero, then $x$ can only be 0. 8. If $h$ is negative, the interval would be empty since $x$ cannot be simultaneously greater than or equal to 0 and less than or equal to a negative number. Final answer: The domain of $x$ is the closed interval $[0, h]$ where $h \geq 0$.