If \(\ \vec{a} \) is a vector of magnitude 50 , collinear with the vector \(\ \vec{b}=6 \hat{i}-8 \hat{j}-\frac{15}{2} \…

If \(\ \vec{a} \) is a vector of magnitude 50 , collinear with the vector \(\ \vec{b}=6 \hat{i}-8 \hat{j}-\frac{15}{2} \hat{k} \) and makes an acute angle with the positive direction of \(\ \mathbf{Z} \) - axis, then \(\ \vec{a} \) is equal to