For a dry system protecting a light hazard attic with the described roof slope and peak height, a minimum calculated design area would typically be around 1,170 ft². This accounts for the attic's geometry and the use of quick response sprinklers, which can effectively cover the area with a smaller design area compared to standard response sprinklers.

References: NFPA 13 guidelines for sprinkler system design criteria, including considerations for attic spaces and the impact of roof slopes on design areas.