; and (B) the assets of the composite plan component and the defined benefit plan component of the plan shall be held in a single trust forming part of the plan under which the trust instrument expressly provides— (i) for separate accounts (and appropriate records) to be maintained to reflect the interest which each of the plan components has in the trust, including separate accounting for additions to the trust for the benefit of each plan component, disbursements made from each plan component’s account in the trust, investment experience of the trust allocable to that account, and administrative expenses (whether direct expenses or shared expenses allocated proportionally), and permits, but does not require, the pooling of some or all of the assets of the two plan components for investment purposes