Answer :
Honestly, I'm not sure how to answer this, but I think this can help you.
Well if 5 and 2 fifths is one third of the total height of the building, then that means to find the total height of the building you need to times 5 2/5 by 3.
(I think F is an answer)
The answer is E, they use the formula 5 2/5 x 3/1 which means that they need 3 wholes of the original 5 2/5.