correct answer is 6.6!!

You are designing a packed bed reactor to contain a total catalyst mass of 17.1 kg. What is the required length of the reactor in meters, expressed to one decimal place? The bulk catalyst density, fraction of solid catalyst, and crosssectional area of the pipe, are 1,624.9kgm3,0.86, and 0.0016m2, respectively. 6.6 margin of error +1.5%