; or (II) the two-year retention trend for personnel performing such duty does not exceed 50 percent. (ii) Maximum amount payable (known as Tier II ) is an amount equal to 68 percent of the amount specified for the fiscal year concerned by paragraph (1)(B) and is payable under agreements for duty by aircraft type category in which— (I) the projected manning level for the fiscal year is between 90 and 95 percent of the required manning level; or (II) the two-year retention trend for personnel performing such duty is between 50 and 55 percent. (iii) Maximum amount payable (known as Tier III ) is an amount equal to 34 percent of the amount specified for the fiscal year concerned by paragraph (1)(B) and is payable under agreements for duty by aircraft type category in which— (I) the projected manning level for the fiscal year is between 95 and 100 percent of the required manning level; or (II) the two-year retention trend for personnel performing such duty is between 55 and 65 percent. (iv) Maximum amount payable (known as Tier IV ) is zero for duty by aircraft type category in which— (I) the projected manning level for the fiscal year is 100 percent or more of the required manning level