In Drosophila, two recessive autosomal mutants, clot eyes (c) and black body (b), are linked and 20 mu apart. A cross is made between double heterozygous wild type flies (CB/cb) and produced 1000 offspring. Assuming that crossing over occurs during the formation of both male and female gametes, how many wildtype offspring would be expected? A) 510
B) 750
C) 563
D) 660
E) 480