A spherical naphthalene ball of 2 mm diameter is subliming very slowly in stagnant air at 25°(C) The change in the size of the ball during the sublimation can be neglecte(D) The diffusivity of naphthalene in air at 25°C is \(1.1 \times 10^{-6} \, m^2/s\). The value of mass transfer coefficient is \( B \times 10^{-3} \, m/s \), where \( B \) (up to one decimal place) is —————.