If r, the coefficient of correlation between n pairs of values (xi, Yi), is positive, then determine whether each of the following statements is true of false:
a. r between (-Xi, - Yi) is also positive.
b. r between (-Xi, Yi) and that between (Xi, Yi) can be either positive or negative.
c. Both the slope coefficients βxy and βxy are positive, where βyx = slope coefficient in the regression of Y on X and βxy = slope coefficient in the regression of X on Y.