How much was atom 2ai2o7si2?

The molar mass of atom 2Al2O7Si2 would be calculated as follows: 2(Al) + 2(O) + 7(O) + 2(Si) = 2(26.98 g/mol) + 2(16.00 g/mol) + 7(16.00 g/mol) + 2(28.09 g/mol) = 404.14 g/mol.