Answer:
Dilution is the prosess where a solution is added more of the solvent to decrease the concentration of the solute. In dilution, the amount of solute does not change, the number of moles are the same before and after dilution.
Mol = # atoms ÷ Avagadaro's number (6.02×10^23)
mol = 2.4×10^24 ÷ 6.02×10^23
mol = 3.986 mol
There are 3 significant digits in 5.40.
(To help understand): Sig figs are just a way of simplifying a number.