Pulverized coal pellets, which may be approximated as carbon spheres of radius r_o = 1 mm, are burned in a pure oxygen atmosphere at 1450 K and 1 atm. Oxygen is transferred to the particle surface by diffusion, where it is consumed in the reaction C + O₂ → CO₂. The reaction rate is first order and of the form N''_O2 = –k C_O2 (r_o), where k''₁ = 0.1 m/s. Neglecting changes in ro, determine the steady-state O₂ molar consumption rate in k mol/s. At 1450 K, the binary diffusion coefficient for O₂ and CO₂ is 1.71 x 10^-4 m²/s.