4.已知a→=(2,−3,1)\overrightarrow{a}=(2,-3,1)a=(2,−3,1),b→=(1,3,0)\overrightarrow{b}=(1,3,0)b=(1,3,0),c→=(0,0,1)\overrightarrow{c}=(0,0,1)c=(0,0,1),则a→⋅(b→+c→)\overrightarrow{a}\cdot (\overrightarrow{b}+\overrightarrow{c})a⋅(b+c)等于((( )))