Consider the function z(x, y) = In(xy) x +1/y . Qla) Find first-order derivatives with respect to x and with respect to y at the point P(1, 1). Q1b) Find all second-order derivatives and check whether mixed derivatives are equal. Rubric: 3 marks if the partial derivative with respect to x has been correctly calculated. 3 marks if the partial derivative with respect to y has been correctly calculated. 5 marks for each correct second-order derivative. 2 marks for each correct partial derivative calculated in point P