If \(\rm \vec{a}= 2\hat i + \hat j +3\hat k, \rm \vec{b}= \hat i + \hat j- 2\hat k \ and \ \rm \vec{c}= 2\hat i + 3\hat k \) are three vectors such that \(\rm \vec{a}+λ\vec{b}\) is perpendicular to \(\rm \vec{c}\), then find the value of λ ?
1
13/8
2
5/4
3
13/4
4
5/8