Many people think that a national lobby's successful fight against gun control legislation is reflecting the will

Question:

Many people think that a national lobby's successful fight against gun control legislation is reflecting the will of a minority of Americans. A previous random sample of 4000 citizens yielded 2250 that are in favor of gun control legislation. How many citizens would need to be sampled if a 90% confidence interval was desired to estimate the true proportion to within 5%?