with the formula z=(xbar - mu)/ (standard deviation/sqrt n)

I am seeing xbar = 352/400 mu=.9 and sqrt n = 400

where do i put the significance level and how do I find the standard deviation?

I am returning back to school after MANY years and have lost all my knowledge from disuse. I would appreciate anyone's help with this. It is probably really simple and I am not seeing it.

An automobile dealership has as one of its performance goals that the proportion of its automobiles sold that are deemed “good value for the money” by the purchasers be at least .90. For a random sample of 400 automobiles sold over the past six months, 352 were deemed by the purchasers to be “good value for the money.” Does this sample data provide evidence that the dealership is not meeting its performance goal? Either use the p-value approach to hypothesis testing or use the significance level approach with ? = .05.