Rachel is planning to run an average of 6.4 miles over three consecutive days. On the first day, she ran 6.6 miles, and on the second day, she ran 6.5 miles. What is the maximum number of miles Rachel can run on the third day without going over the planned average of 6.4 miles per day? a 5.1
b 6 1
c 6.7
d 6.55​