A rigid L-shaped lever arm is pivoted at point $P$. Three forces act on the lever arm, as shown in the diagram. What is the magnitude of the resultant moment produced by these forces about point $P$?
- A$15\,\text{N m}$
- B$20\,\text{N m}$
- C$35\,\text{N m}$
- D$75\,\text{N m}$