XYZ Inc. earned $$100$ million last year and paid out $20\%$ of its earnings as dividends. The firm also has bought back $$180$ million of stock over the past four years, in varying amounts each year. The firm is in stable growth, expects to grow $5\%$ a year in perpetuity, and has a cost of equity of $15\%.$

Assuming that the dividend payout ratio will not change over time, estimate the value of equity $($in $million$).$