Table 2. The function c(p) of the punishment costs.

p	0	1	2	3	4	5	6	7	8	9	10
c(p)	0	1	2	4	6	9	12	16	20	25	30

p is the number of punishments submitted by a player to another player. c(p) is a function of the punishment costs is adopted from [1].