  A multiple access channel and a point-to-point channel sharing the same
medium for communications are considered. We obtain an outer bound for the
capacity region of this setup, and we show that this outer bound is achievable
in some cases. These cases are mainly when interference is strong or very
strong. A sum capacity upper bound is also obtained, which is nearly tight if
the interference power at the receivers is low. In this case, using Gaussian
codes and treating interference as noise achieves a sum rate close to the upper
bound.
