The Department of Computer Science provides all users of its systems with home directory and e-mail space through its Computer Services Recharge Center. The department also provides research projects additional backed up disk space on departmental servers. Fees for this disk space are based on a four-year useful lifetime for the servers, with the first such period beginning 1/1/2005 and ending 12/31/2008. The current rate is $30/gigabyte for four years' use of the space. Disk space is currently available in 8, 16, and 32 gigabyte increments. The fee is prorated monthly for disk space obtained after 1/1/2005 and is also prorated for grants that end before 12/31/2008. For example, if a project whose grant ends on 12/31/2007 wants to obtain 8 GB starting on 1/1/2006, the charge is (2 years) X ($30/1 GB for 4 years) X (8 GB) = $120. As a second example, if a project whose grant ends on or after 12/31/2008 wants to obtain 8 GB starting on 1/1/2004, the charge is (4 years) X ($30/1 GB for 4 years) X (8 GB) = $240.