If the vectors $\bar {AB}=-3 \bar {i}+ 4 \bar {k}$ and $\bar {AC}=5 \bar {i}-2 \bar j+4 \bar {k} $ are the sides of a triangle ABC, then the length of the medium through A is

Question

\[\begin {array} {1 1} (a)\;\sqrt {14} & \quad (b)\;\sqrt {18} \\ (c)\;\sqrt {25} & \quad (d)\;\sqrt {29} \end {array}\]