Let `vec a=hat i+hat j+hat k and vec b=i and vec c=c_1 hat i + hat c_2 j +c_3 hat k` Then(a) if `c_1 = 1 and c_2=2` , find `c_3` which makes ` vec a , vec b, vec c ` coplanar(b) if `c_2 = -1 and c_3= 1` , show that no value of `c_3` can makes ` vec a , vec b, vec c ` coplanar.