Which of the following production functions exhibit constant returns to scale? In each case, y is the output, and K and L are the inputs.
(1) y = K¹/²・L¹/³
(2) y = K¹/⁴・L³/⁴
(3) y = K¹/²・L¹/²
(4) y = 2K+3L.
a. 3 and 4
b. 2 and 3
c. 2 and 4
d. 1 and 3
e. a and 4