10. Minimum Operating Expense Available Balance Revenue Requirement Calculation; Replenishment of Operating Account.

The Department will covenant to include in its revenue requirements amounts sufficient to cause a "Minimum Operating Expense Available Balance" to be on deposit in the Operating Account. The Minimum Operating Expense Available Balance is to be calculated by the Department at the time of each determination of a revenue requirement. "Minimum Operating Expense Available Balance" for so long as the Department continues to purchase the Residual Net Short, may be an amount up to and including $1,000,000,000, and thereafter will be an amount equal to the largest projected difference between the Department's projected operating expenses and the Department's projected Power Charge revenues during any one month period during the then current revenue requirement period, taking into account a range of possible future outcomes.

The Indenture may provide that, if on any date the Operating Account balance falls below specified levels, the Department will submit a new Revenue Requirement to the Commission providing for revenues sufficient to restore the Operating Account to the Minimum Operating Expense Available Balance within periods permitted for restoration to be specified in the Indenture. The last day of any required period for restoration which may be specified in the Indenture shall be no sooner than 225 days following the submission of such Revenue Requirement to the Commission. The time period during which the Commission is required to act in response to any such submission under the Rate Agreement will not be affected by such provision.