The Rate at Which a Rumor Spreads Through an Alpine

The rate at which a rumor spreads through an Alpine village of 500 residents is jointly proportional to the number of residents who have heard it and the number who have not. Initially, 15 residents heard the rumor, but 4 days later this number increased to 80. Find the number of people who will have heard the rumor after 1 wk. Round the answer to the nearest integer. __________ people