How would I find the correlation coefficient? I'm not sure where to even start.

Problem 8. An emergency service wishes to determine whether a relationship exists between the outside temperature and the number of emergency calls it receives for a 7-hour period. The data are shown. Temperature x No. Of calls y 25 7 10 4 27 8 30 10 33 11 8a) Find the correlation coefficient r? Show all your steps. Do not round off. (6 points)