An IQ test is designed so that the mean is 100 and the standard deviation is 12 or the population of normal adults. Find the sample size necessary to estimate the mean IQ score of statistics students...

90​% confidence that the sample mean is within 2 IQ points of the true mean. Assume that  σ=12 and determine the required sample size using technology. Then determine if this is a reasonable sample size for a real world calculation.

What is the required sample size?

Can you please really break this down for me. I don't even know how to find the critical value with this problem.