If the serial numbers are randomly distributed in some finite span, and you have the serial number of three tanks, say: a: 000001 b: 000101 c: 1000

If the serial numbers are randomly distributed in some finite span, and you have the serial number of three tanks, say: a: 000001 b: 000101 c: 100000 What is the probability that c is not the highest serial number and that there are 1000 total tanks. How many tank serial numbers would we need before those probabilities get > 90%, > 95%?