How would I work this problem?

Use Lagrange multipliers to find the maximum and minimum values of f(x,y) = e 4xy (if they exist) subject to the constraint x2 + y2 = 28. If there is a maximum value, what is it? Select the correct choice below and, if necessary, fill in the answer box to complete your choice. O A. The maximum value is (Type an exact answer in terms of e.) O B. There is no maximum value