If you consider M as a contant then there is no exact maximim value.
Here the maximum is not an exact value. It will be infinity. So we can say the answer is a.
You need to maximize the objective function M, hence, you should first write this function in terms of x or in terms of y. You should consider other conditional relation to help the objective function to be expressed in terms of x or in terms of y.
Since the conditional relation misses, you should maximize the given function finding its partial derivatives and setting them equal to zero such that:
`M_x = 6 != 0` (differentiate with respect to x, considering y as constant)
`M_y = 3 != 0` (differentiate with respect to y, considering x as constant)
Hence, evaluating the partial derivatives yields that the objective function cannot be maximized, under the given conditions.