Find percent of phosphorus pentoxide in plant food sample

Question

An analytical lab needed to determine the content of phosphorus in a commercial sample of plant food. The phosphorus in a 4.258 g sample of this plant food was converted to PO₄^3- and precipitated by adding 50.00 mL of 0.0820 M AgNO₃. The excess AgNO₃ was then titrated using 4.06 mL of 0.0625 M KSCN. What was % P₂O₅ in the original plant food sample?

P₂O₅ + 9 H₂O → 2PO₄^3- + 6H₃O⁺

2PO₄^3- + 6 Ag⁺ → 2Ag₃PO_4(s)

Ag⁺ + SCN^- → AgSCN_(s)