Statement I: If $\theta$  is angle between two lines whose Dc’s are $(l_1,m_1,n_1)$  and  $(l_2,m_2,n_2)$  then  $\cos \theta =l_1{l}_2+m_1{m}_2+n_1{n}_2$ 
Statement II: If  $(l_1,m_1,n_1)$  and $(l_2,m_2,n_2)$ are Dc’s of two lines then  

${(l_1{l}_2+m_1{m}_2+n_1{n}_2)}^2+{(l_1{m}_2-l_2{m}_1)}^2+{(m_1{n}_2-m_2{n}_1)}^2+{(n_1{l}_2-n_2{l}_1)}^2=1$
Statement III: The triplets $(\frac{1}{7},\frac{4}{7},\frac{2}{7})$  be the Dc’s of a line 
which of the above statement is correct