  YBaCuO_7 is a trilayer material with a unit cell consisting of a CuO_2
bilayer with a CuO plane of chains in between. Starting with a model of
isolated planes coupled through a transverse matrix element, we consider the
possibility of intra as well as interplane pairing within a nearly
antiferromagnetic Fermi liquid model. Solutions of a set of three coupled BCS
equations for the gap exhibit orthorhombic symmetry with s- as well as d-wave
contributions. The temperature dependence and a-b in plane anisotropy of the
resulting penetration depth is discussed and compared with experiment.
