Which number gives the atomic mass of the element?

In which of these cases are the two wave points considered to be in phase with each other?

Tin has ten stable isotopes. the heaviest, 124sn, makes up 5.80% of naturally occuring tin atoms. how many atoms of 124sn are present in 82.0 g of naturally occurring tin? what is the total mass of the 124sn atoms in this sample?

Type the letter that represents the correct location for each particle type below.