Electronic devices found in integrated circuits are composed of very high purity silicon to which has been

Question:

Electronic devices found in integrated circuits are composed of very high purity silicon to which has been added small and very controlled concentrations of elements found in Groups IIIA and VA of the periodic table. For Si to which has had added 6.5 × 1021 atoms per cubic meter of phosphorus, compute

(a) The weight percent and

(b) The atom percent of P present?