Hypothesis Testing Help

I have read everything I can on hypothesis testing but I am struggling with this one question. I just need someone to explain it to me. Just where I need to start.
Williams Coke Distributor labels its coke bottles 32 ounces. The Weights and Measures department randomly samples 50 bottles and finds a sample mean of 31.80 ounces with a standard deviation of .75. With a significance level of .01 test this claim of cheating by Weights and Measures.

I don't understand whether to use a t score or z score. how to get that score and then how the sign level ties in (to find the critical value??) and ultimately to reject or fail to reject. Any guidance would be much appreciated

As Sample size is more than 30 you can use Z-test to test the mean
The following things has to be done

1.You will to decide whether it is one tailed test or two-tailed test

(Your case the choice will be one tailed test as your testing against the claim that distributor is cheating i.e. mean < 32)

2.you can calculate the z statistics by

z = (sample mean - population mean under Null hypothesis)/SE of mean

3.compute your p value
4.divide the p value by 2 as it is a one tailed test
5. You will have to compare this pvalue with the level of significance you have fixed.
6. If your computed p-value is than the significance level then you can reject the null hypothesis and accept the alternative hypothesis