(a) (0.5 points) What kind of returns to scale does this production function exhibit? f(zl, 22) = 21 l 235. 03. constant returns to scale Ob. Increasing returns to scale c. Decreasing returns to scale Od. Cannot be determined from the given information (b) (1 point) At (21, :52) = (4, 1), the technical rate of substitution between the two inputs 21 and 22 is |:| [note: it is a positive number]