Calculate hololive Dreams gacha probabilities. Estimate the chance of getting at least N hits based on target rate, number of pulls, or stones.
Assuming a target rate of 0.6666%, 250 stones per pull, and 8,200 stones per pack:

1. What is the probability of getting at least 1 ★5 in one pack?
   A: 19.267%
2. What is the probability of getting at least 1 ★5 in 10 pulls?
   A: 6.470%
3. What is the probability of getting at least 1 ★5 in 100 pulls?
   A: 48.769%
4. What is the probability of getting at least 1 ★5 with 2,500 stones?
   A: 6.470%

Note: Pity / ceiling is not considered