Resultant Moment Vector $\boldsymbol { M } _ { R }$

resultant moment vector $\boldsymbol { M } _ { R }$ at point O in Problem 2.2 is (in N ∙ m) :

A) $12 j + 18 k$
B) $- 15 i + 12 k$
C) $18 j + 12 k$
D) $- 12 i + 18 j$