A gas stream with 2.01 mol % ammonia is to be scrubbed in a counter-current isothermal packed bed absorber using pure water to reduce its concentration to 0.01 mol %. Assume that dilute conditions apply, operating line is linear and the mass transfer coefficients are constant throughout the column. The liquid and the gas flows inside the absorber (in kmol m⁻² h⁻¹) are 1000 and 200, respectively. The equilibrium relationship is y = 0.9x, where y is the mole-fraction of ammonia in the gas phase and x is that in the liquid. Under these conditions, the height of overall gas transfer unit (H_tOG) is 0.8 m and the number of overall gas transfer units (N_tOG) is given by the integral N_tOG = ∫_y1^y2 dy/(y−y*). Which one of the following is the minimum length of the packing (in m) necessary to achieve the desired scrubbing?