please help, thx

To estimate the difficulty of the final exam, the teaching team has designed a mock exam that is at the same level of difficulty as that of the real exam. If the average mark for this mock exam is lower than 60, that would indicate that the level of difficulty is too challenging for all students. In order to find out the difficulty level of the mock exam, the teaching team randomly invited a sample of 20 students to take the mock exam. The average mark of the sample is 66, with a sample standard deviation of 10. Supposing that the score is normally distributed, what hypothesis (or hypotheses) should the teaching team raise if they want to make sure that the level of difficulty for the exam is not too challenging