Let \({\rm{\vec \alpha }} = {\rm{\hat i}} + 2{\rm{\hat j}} - {\rm{\hat k}},{\rm{\;\vec \beta }} = 2{\rm{\hat i}} - {\rm{\hat j}} + 3{\rm{\hat k}}\) and \({\rm{\vec \gamma }} = 2{\rm{\hat i}} + {\rm{\hat j}} + 6{\rm{\hat k}}\) be three vectors. If \({\rm{\vec \alpha }}\) and \({\rm{\vec \beta }}\) are both perpendicular to the vector \({\rm{\vec \delta }}\) and \({\rm{\vec \delta }} \cdot {\rm{\vec \gamma }} = 10\) , then what is the magnitude of \({\rm{\vec \delta }}\) ?

• A. √3 units
• B. 2√3 units
• C. √3/2 units
• D. 1/√3 units