A silicon substrate \(10 \mathrm{~cm}\) long is exposed to a gas stream containing an arsenic precursor so that a GaAs film can be deposited on the surface. Estimate the mass-transfer coefficient, and the average rate of mass transfer. If the deposition is mass-transfer-controlled, how would the deposit thickness vary along the length of the plate? In practice, uniform deposition is needed and the flat plate may therefore not be a good arrangement under these conditions.