Verified answer

756

you get this by using the general relationship t x (std errors) = b (want t std errors to equal the margin of error b)

where t is the critical value associated with the confidence level required and b is the margin of error required

if you work the general relationship and solve for n, you get n=(t/b)^2 (variance)

here, t=1.645 for 90% confidence; b=.03; and variance of a proportion is (assuming worst case p=.5) = p(1-p) = .5(1-.5)=.25

So n=(1.645/.03)^2 (.25) = 751.6, and round up to get n=752