which percent of cell overlap is recommended for 2.4 GHz and 5 GHz access points?

To provide efficient roaming between the cells, which percent of cell overlap is recommended for 2.4 GHz and 5 GHz access points?

A.
5 to 10 percent for both 2.4 GHz and 5 GHz

B.
10 percent for both 2.4 GHz and 5 GHz

C.
20 percent for 2.4 GHz and 15 to 20 percent for 5 GHz

D.
20 percent for 2.5 GHz and 10 percent for 5 GHz