The Verhulst's logistic model has been applied to natural growth of halibut population in specific areas of Pacific Ocean. Let NN, measured in kg, be the total mass (or biomass) of halibut population at time tt. The parameters in logistic equation are approximated to have the values r=0.71: per: year and K=80.5times10^6: kg. If initial biomass is N_0=0.25K, N0=0.25K, Find out the biomass 2 years later; as well, Find out the time tauτ for which Nleft(tauright)=0.75K.