CompTIA Server+

Answer - B - To install a 6U server, 10.5 inches of room is required on the server rack.

Key Takeaway: U is a common unit of measurement in rack systems. Rack-mount cases typically come in 1U, 2U, 4U, or 5U sizes. One U is 1.75 inches high and is the smallest unit that can be placed into a rack. A full rack is 42 Us in height. The server case may be any size, but is measured in multiples of the U size designation.