need explanation for B

QUESTION 1 The Restaurant management council of a certain city wanted to study the salaries of the restaurant workers in the city. They divided the city into four regions (north, south, east, and west) and selected random sample of restaurants from each region. The salary data is given below: Salary SK Frequency 15 - 24.5 25 -34.5 35 -44.5 45 -54.5 55 - 64.5 a) What type of sampling was used to gather the data? bj What is the class width of the frequency distribution? c) What are the class boundaries for the class 45 - 54.5 (SK) ? N+$10 (Mac). E x3 X z