For  N2+3H2→2NH3, rates of disappearance of N2 and  H2 and rate of appearance of NH3 respectively are a, b and c, then

For every '1' mole of N2 disappearing, '3' moles of H2 disappears and '2' moles of NH3 forms.This indicates rate of disappearance N2 < Rate of appearance of NH3 < Rate of disappearance of H2a < c < b