A large corporation's electricity bill amounts to $400 million. During

A large corporation's electricity bill amounts to $400 million. During the next 10 years, electricity usage is expected to increase by 75%, and the estimated electricity bill 10 years hence has been projected to be $920 million. Assuming electricity usage and rates increase at uniform annual rates over the next 10 years, what is the annual rate of inflation of electricity prices expected by the corporation?