Answer
$(a)\space B=10.4\space units$
$(b)\space C=12\space units$
Work Step by Step
Let's take due north to be the direction of the +y, and due east to be the direction of the +x. The components of the resultant C are A and B. The angle that C makes with the x-axis is then $\theta=tan^{-1}(\frac{B}{A})$
(a) $B=Atan\theta=6\times tan60^{\circ}= 10.4\space units$
(b) $|C|=\sqrt {A^{2}+B^{2}}=\sqrt {(6)^{2}+(10.4)^{2}}=12\space units$
