Two lakes have populations of fish, but the conditions are quite different in these lakes. In the first lake, the fish population is growing and satisfies the differential equation 0.7y where t is time in years. At time t = 0 there were 450 fish in this lake. In the second lake, the population is dying due to pollution. Its population satisfies the differential equation dy dt dy dt and initially there were 3500 fish in this lake. At what time will the fish populations in the two lakes be identical?