A population of the land snail Cepaea vindobonensis shows variation in the intensity of its shell pigmentation determined by one locus with two alleles, N and n: NN individuals have dark shells, nn individuals have light shells, and Nn individuals have an intermediate phenotype. We construct a laboratory population with the following composition: 60 NN, 70 Nn, and 80 nn. In the following generation we introduce 30 individuals from a source population in Hardy-Weinberg equilibrium with a frequency of N of p = 0.621. Assuming random mating, what do you expect the frequency of N to be in the following generation (i.e., two generations after the start of the experiment)? (Hint: Continent-island migration; see formula sheet.)