  We report photometric and spectroscopic observations of the black hole binary
GRO J1655-40 in complete quiescence. In contrast to the 1995 photometry, the
light curves from 1996 are almost completely dominated by ellipsoidal
modulations from the secondary star. Model fits to the light curves, which take
into account the temperature profile of the accretion disk and eclipse effects,
yield an inclination of i=69.50 +/- 0.08 degrees and a mass ratio of Q=2.99 +/-
0.08. The precision of our determinations of i and Q allow us to determine the
black hole mass to an accuracy of approximately 4% (7.02 +/- 0.22 solar
masses). The secondary star's mass is 2.34 +/- 0.12 solar masses. The position
of the secondary on the Hertzsprung-Russell diagram is consistent with that of
a 2.3 solar mass star which has evolved off the main sequence and is halfway to
the start of the giant branch. Using the new spectra we present an improved
value of the spectroscopic period (2.62157 +/- 0.00015 days), radial velocity
semiamplitude (228.2 +/- 2.2 km/sec), and mass function (3.24 +/- 0.09 solar
masses). Evolutionary models suggest an average mass transfer rate for such a
system of 3.4E-9 solar masses per year (2.16E+17 grams per second), which is
much larger than the average mass transfer rates implied in the other six
transient black hole systems, but still barely below the critical mass transfer
rate required for stability.
