A company sends an email survey to 3,500 customers and asks them to rate their customer satisfaction on a scale of 1 to 11. Of the customers who receive the email, 2,500 have been customers for less than 1 year and 1,000 have been customers for more than one year. Of the <1 year customers, 15% answer the survey; of the >1 year customers, 25% answer the survey. The <1 year customers post an average rating of 5.0 and the >1 year customers post an average rating of 8.5. Required:
a. Which group provided more responses?
b. What is the overall average rating from the survey?