  We show a duality of branes in the topological B-model by inserting two kinds
of the non-compact branes simultaneously. We explicitly derive the integral
formula for the matrix model partition function describing this situation,
which correspondingly includes both of the characteristic polynomial and the
external source. We show that these two descriptions are dual to each other
through the Fourier transformation, and the brane partition function satisfies
integrable equations in one and two dimensions.
