- INSTANCE:
Disjoint sets
and, for any ,
,
and ,
a nonnegative capacity
*c(x,y)*. - SOLUTION:
A system of representatives
*T*, i.e., a set*T*such that, for any*i*, . - MEASURE:
The capacity of the system of representatives, i.e.,
.

*Bad News:*Not approximable within for some*p>0*unless NP [67].*Comment:*Does not admit a PTAS.