16. 已知a→=(2,−1,3),b→=(−1,4,−2),c→=(4,5,λ)\overrightarrow{a}=(2,-1,3),\overrightarrow{b}=(-1,4,-2),\overrightarrow{c}=(4,5,\lambda )a=(2,−1,3),b=(−1,4,−2),c=(4,5,λ),若a→,b→,c→\overrightarrow{a},\overrightarrow{b},\overrightarrow{c}a,b,c共面,则实数λ\lambdaλ的值为((( )))