Question 3.4 The normal distribution is written as $f(x; \mu, \sigma) = \frac{1}{\sqrt{2\pi\sigma^2}} exp \left[ -\frac{(x-\mu)^2}{2\sigma^2} \right]$ where x is the random variable, μ is the mean and σ² is the variance. Calculate the gradient and Hessian matrix of ln f (x; μ, σ) with respect to its parameters μ and σ².