Structure OBCD is built in at point $O$ and supports a $50$ lb cable force at point $C$ and $100$ and $190$ lb vertical forces at points $B$ and $D,$ respectively.

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Using a vector approach, determine the moment of these forces about point $B.($Round the final answers to four decimal places. Include a minus sign if necessary.$)$

The moment of the forces about point $B$ is $($ hat$(i)+$ hat$(k).$