I have some questions in chemistry

1.) To the nearest atomic mass unit, what is the formula mass of aluminum oxide, Al2O3?


2.) To the nearest gram, what is the molar mass of Al2O3?


3.) How many moles are present in 408 grams of Al2O3?


4.) How many molecules are present in 408 grams of Al2O3?


It would be great if you showed your calculations to show me how it's all done!
Thanks if you help!

1) Al2O3
Al2= 2 * 27= 54
O3= 3 * 16= 48
formula mass is 54+48 = 102
3) 5