Human blood type is determined by three alleles IA, IB, and IO. The alleles IA and IB are co-dominant to each other, and both are dominant to IO. Within a large, randomly mating population (540,000 individuals), the frequencies for the blood type alleles are 0.3 for the IA allele, 0.6 for the IO allele, and 0.1 for the IB allele. What percentage of the type A people are heterozygotes (IAIO)?