SIGAR may apply other charges, including the following:

(a) Special charges. SIGAR shall recover the full cost of providing special services, such as sending records by an overnight delivery service, to the extent that SIGAR elects to provide them.

(b) Interest charges. SIGAR may begin assessing interest charges on an unpaid bill starting on the 31st day following the day on which the FOIA Officer sent the billing. Interest shall be charged at the rate prescribed in 31 U.S.C. 3717 and will accrue from the date of billing.

(c) Aggregating requests. When the FOIA Officer reasonably believes that a requester or a group of requesters acting in concert is attempting to divide a request into a series of requests within a 30-day period for the purpose of avoiding fees, the FOIA Officer shall aggregate those requests and charge accordingly.