For all real x, the vectors \(\vec{a}\) = cxî - 6ĵ + 3k̂ and \(\vec{b}\) = xî + 2ĵ +2cxk̂ makes an obtuse angle with each other. Then, the value of c must satisfy which one of the following conditions?
1
0 < c < 4/3
2
-4/3 < c < 0
3
c > -4/3
4
c > 4/3