Two waves are simultaneously passing through a string and their equations are:
${\text{y=A}}_{\text{1}}\text{sink}\left(\text{x-vt}\right){\text{,y}}_{\text{2}}{\text{=A}}_{\text{2}}\text{sink}\left({\text{x-vt+x}}_{\text{0}}\right)$ . Given amplitudes  ${\text{A}}_{\text{1}}{\text{=12mm\hspace{0.17em}and\hspace{0.17em}A}}_{\text{2}}{\text{=5mm,\hspace{0.17em}x}}_{\text{0}}\text{=3.5cm}$  and wave number  ${\text{k=6.28cm}}^{\text{-1}}$ . The amplitude of the resulting wave will be __________mm.