please help me answer this question

1. {4 points) Do the following production functions exhibit increasing, constant, or decreasing returns to scale in K and N? Assume z > 0 is a constant and make sure to show your work. Y = zK2/3N2/3 Y = K1/3N1/2 Y = K + N Y = K1/3N2/3 + z 9957'!\