Suppose Fiat recently entered into an Agreement and Plan of Merger with Case for $$4\mathrm{.}3$ billion. Prior to the merger, the market for four$-$wheel$-$drive tractors consisted of five firms. The market was highly concentrated, with a Herfindahl$-$Hirschman index of $3,100.$ Case's share of that market was $20$ percent, while Fiat compromised just $14$ percent of the market. If approved, by how much would the postmerger Herfindahl$-$Hirschman index increase?