/7 1. For the function below, nd the optimum value of 2 (that is, maximum or minimum) subject to the given constraint (a) by the method of direct substitution, and (b) by setting the slope of the iso-z section equal to the slope of the constraint. (c) Attempt to assess informally the shapes of the two surfaces and whether the optimum is a maximum or minimum of z. z = x3 + 10322 subject to the constraint 3: = 40 0.5x