Suppose There Are Four Banks in a Local Community

Suppose there are four banks in a local community.Each of these banks has 25 percent of the deposits in this community.Calculate the change in the Herfindahl-Hirschman Index (HHI) if two of these banks merge.

A) 625
B) 1,000
C) 1,150
D) 1,200
E) 1,250