​Michael, an Internet service​ provider, bought an existing business worth ​$200 comma 000 on December​ 31, 2017. During 2018​, his business grew and he bought ​$400 comma 000 of new servers. The market value of his older servers fell by ​$150 comma 000. What was​ Michael's gross​ investment, depreciation and net investment during 2018​?