Y inc. is planning to invest ia a $$10$million project that spans over $6$years$.\text{'}$

$$maintenace costs of $$642645$ that starts from $2$nd year, and revenues of $$6\mathrm{.}875$million per year starting from $3$rd year. if the sales taxon the revenu is $20\%$

$$what is IRR? I need to see the formual not an excel function.