If x : y : z = 1 : 2 : 3, what is the value of $$\left(\frac{x^{2}+2y^{2}+z^{2}}{3x^{2}-2y^{2}+4z^{2}}\right)$$

A

$$\frac{15}{31}$$

B

$$\frac{16}{31}$$

C

$$\frac{18}{31}$$

D

$$\frac{19}{31}$$