Let $$x_{1}, x_{2} ... x_{n}$$ be a set of observations and $$f_{1}, f_{2} ... f_{n}$$ be their frequencies. If $$y_{i} = 3x_{i} + K$$ then $$\frac{\sum (y_{i} - \overline{y})^{2}f_{i}}{\sum f_{i}}$$

A

$$\frac{3\sum f_{i}(x_{i} - \overline{x})^{2}}{\sum f_{i}}$$

B

$$\frac{9\sum f_{i}(x_{i} - \overline{x})}{\sum f_{i}}$$

C

$$\frac{9\sum f_{i}(x_{i} - \overline{x})^{2}}{\sum f_{i}}$$

D

$$\frac{3\sum f_{i}(x_{i})^{2}}{\sum f_{i}}$$