The variance of a uniform (or rectangular) distribution, denoted $U(a, b)$, where $a$ and $b$ are the minimum and maximum values respectively, is given by:

$\text{Var}(X) = \frac{(b - a)^2}{12}$

Therefore, the correct answer is:

a) $\frac{(b - a)^2}{12}$

Would you like more details or have any questions? Here are some related questions to expand your understanding:

1. How do you derive the variance formula for a uniform distribution?
2. What is the mean of a uniform distribution $U(a, b)$?
3. How would the variance change if the distribution was not uniform but normal with the same $a$ and $b$?
4. Can you provide an example calculation of variance for a uniform distribution with specific values of $a$ and $b$?
5. How is the uniform distribution used in practical applications?

Tip: For any continuous uniform distribution, the variance formula $\frac{(b - a)^2}{12}$ can help you quickly determine the spread of the distribution, which is useful in many statistical analyses and simulations.