It has been estimated that the number of people who will see a newspaper advertisement that has run for x consecutive days is of the form N(t)=T-(t/2x) for x greater than or equal to 1 where T is the total readership of the newspaper. If a newspaper has a circulation of 200,000 an ad that runs for x days will be seen by N(x)=200,000-(100,000/x) people. Find how fast the number of potential customers is growing when this ad has run for 5 days.