Based on the data given, we have a small size as a sample since n = 11.
Other given data are the mean = 58, sample SD = 17.9, and a population mean of 81.2. With a sample size small and unknown population standard deviation, the test statistic appropriate for this would be t-test. The formula is:
Knowing the data given above, let's apply it to the formula.
The test statistic is -4.299 and a p-value of 0.0008. (one-tail)