A supermarket ran a linear regression of the number of cans of soup sold (y) against daily temperature (x) in degrees Fahrenheit, for an entire year's worth of data. The resulting regression equation was y = 300 - 1.5 x. The R2 for the regression was 0.25. What was the correlation between temperature and cans of soup sold?

a. 0.548

b. -0.5

c. 0.5

d. 2.25

e. It is not possible to work out the correlation without knowing the RMSE for the regression.