Two blocks of masses m and M are connected by means of a metal wire of cross-sectional area A passing over a frictionless fixed pulley as shown in the figure. The system is then released. If M = 2m, then the stress produced in the wire is:

A

$$\frac{2mg}{3A}$$

B

$$\frac{4mg}{3A}$$

C

$$\frac{mg}{A}$$

D

$$\frac{3mg}{4A}$$