A method for providing an estimate for a defined building control system comprises displaying on a user interface a plurality of areas in which the defined building control system would be installed. This computation circuit comprises a computation unit which performs additions of n-digit data; an m-digit updown counter; and a control circuit which uses the updown counter to generate the upper m digits of the computation result. When the first determination is negative, a second determination is performed to determine whether to provide admission to dedicated resources.