Boron has 5 protons, 5 electrons and 6 neutrons for the most common isotope. This determines that it has a neutral charge.
the balanced equation for the combustion of ethane is as follows
2C₂H₆ + 7O₂ --> 4CO₂ + 6H₂O
molar ratio of C₂H₆ to H₂O is 2:6
this means that when 2 mol of C₂H₆ react 6 mol of H₂O are produced
for every 1 mol of C₂H₆ that reacts thrice the number of moles of H₂O are produced
therefore when 1.4 mol of C₂H₆ reacts - 3 x 1.4 = 4.2 mol of H₂O are produced
the answer is 4.2 mol