1. A realtor is developing a rental housing and retail area. TIle housing area consists of efficiency apartments, duplexes, and single-family homes. Maximum demand by potential renters is estimated to be 500 efficiency apartments, 300 duplexes, and 250 single-family homes, but the number of duplexes must equal at least 50% of the number of efficiency apartments and single homes. Retail space is proportionate to the number of home units at the rates of at least 10 ft2

, 15 ft2

, and 18 ft2 for efficiency, duplex, and single family units, respectively. However, land availability limits retail space to no more than 10,000 ft2. The monthly rental income is estimated at $600, $750, and $1200 for efficiency-, duplex-, and single-family units, respectively. The retail space rents for $1001ft2

. Determine the optimal retail space area and the number of family residences.