After vaccination, 70% of the people are immune from the disease.

Suppose we select N people randomly from the city's population with replacement. Let X be random variable recording the number of people among them with immunity.We find that 65% of them are immune.What is the smallest value of N

that would make this sample one of the 10% most unlikely samples, i.e.its 90% confidence interval does not contain the true mean of X ?