Question 4 (1.5 points) (a) (0.5 points) What kind of returns to scale does this production function exhibit? f(zl , 22) = 21 + 235. 0a. Decreasing returns to scale Ob. Cannot be determined from the given information 00. Constant returns to scale Od. Increasing returns to scale (b) (1 point) At (21, 22) = (4, 25), the technical rate of substitution between the two inputs 2.1 and 22 is D [note: it is a positive number]