Provide an electron-pushing mechanism for the S_N2 reaction shown below.

Detailed electron-pushing mechanism for SN2 reaction with bromine and cyanide.

SN2 reaction mechanism illustrating electron flow from bromine to cyanide.

Illustration of SN2 reaction showing electron-pushing from bromine to cyanide.

SN2 reaction mechanism with electron-pushing arrows for bromine and cyanide.

Provide an electron-pushing mechanism for the SN2 reaction shown below.