The most difficult or unexpected thing was that they contact you right immediately leaving you no time to prepare, so before you apply take you're time to prepare and they apply. other than that this question was pretty difficult:
An analyst at Facebook is conducting a satisfaction survey sampling from a list of 10,000 new users. The list includes 2,500 French users, 2,500 German users, 2,500 Italian users, and 2,500 Portuguese users. The analyst select a sample of 400 users, by randomly sampling 100 users of each country. is this an example of a simple random sample?