In most human populations, the frequency of the sickle anemia is negligible . However, in some equatorial African populations. as many as 10% newborns have sickle cell anemia. Assuming that most individuals with sickle cell anemia die before reaching reproductive age (fitnessW(ss)=0) and setting the finess of non-sickle homozygotes W(SS)=1, calculate the fitness advantage to heterozygous "carriers"