  In communication networks, cooperative strategies are coding schemes where
network nodes work together to improve network performance metrics such as
sum-rate. This work studies encoder cooperation in the setting of a discrete
multiple access channel with two encoders and a single decoder. A node in the
network that is connected to both encoders via rate-limited links, referred to
as the cooperation facilitator (CF), enables the cooperation strategy.
Previously, the authors presented a class of multiple access channels where the
average-error sum-capacity has an infinite derivative in the limit where CF
output link capacities approach zero. The authors also demonstrated that for
some channels, the maximal-error sum-capacity is not continuous at the point
where the output link capacities of the CF equal zero. This work shows that the
the average-error sum-capacity is continuous when CF output link capacities
converge to zero; that is, the infinite derivative of the average-error
sum-capacity is not a result of its discontinuity as in the maximal-error case.
