Function (0) with a p-dimensional vector 0 is maximised at 0 if (6) dej = 0 for j = 1, op and a. All the elements of the observed information matrix J(, y) are positive. b. All the elements of the observed information matrix J(, y) are negative. C. The observed information matrix J(, y) is negative definite. d. The observed information matrix J(, y) is positive definite.