Suppose the Iowa City Council reads Raj Chetty's research and decides they want to prioritize increasing upward mobility for low-income children. Which zoning choice would increase upward mobility?
a) Zoning most of the city for single-family housing, with limited area zoned for multi-family
b) Zoning half the city single-family housing and the other house multi-family, but in very well-defined areas
c) Removing the distinction between "single-family" and "multi-family". Areas zoned simply "residential" could be developed with single-family or multi-family structures
d) Making more areas zoned for public use