with covariance matrix V (bOLS) = σ (XX) Let us, however, assume more generally that ε ∼ Nn(0,Σ), where the error-covariance matrix Σ is symmetric and positive-definite. Different diagonal entries in Σ correspond to non-constant error variances, while nonzero off-diagonal entries correspond to correlated errors. Suppose, for the time-being, that Σ is known. Then, the log-likelihood for the mode...