hello

please explain this question to me

i do not understand how to do it.

A pharmaceutical company wants to test the effectiveness of a new drug for a particular infectious disease. In a sample of patients with the disease, 24 were randomly assigned to receive the new drug, while the remaining 16 patients were given a placebo. The length of time the infectious disease lasted was recorded by a doctor for each patient. The sample mean for the group taking the new drug was found to be 6.5 days and for the control group (taking the placebo) the mean was 7.125 days. The (population) standard deviation of recovery times for people with the infectious disease is known to be 1.2 days. Test the claim that the drug reduces the time that an infectious disease lasts, at the 5% significance level. What is the p-value for this test? What assumptions do you need to make for this test to be valid?

many thanks