Match List-I with List-II and select the correct answer:

List-I	List-II
a. Coefficient of determination	1. $${\gamma _{xy}}\frac{{{\sigma _x}}}{{{\sigma _y}}}$$
b. Spearman's rank correlation coefficient	2. $$1 - \frac{{6\sum {{d^2}} }}{{n\left( {{n^2} - 1} \right)}}$$
c. Regression coefficient of $$x$$ on $$y$$ variable	3. $$\frac{{\sum {xy} }}{{n\,{\sigma _x}\,{\sigma _y}}}$$
d. Karl Pearson's formula of calculating $$\gamma $$	4. $${\gamma ^2}$$