Three coplanar forces act on a particle, as shown in the diagram below:

Given that the resultant of these three forces acts purely in the horizontal direction, find the magnitude of the force F F\,F to 1 decimal place.
4.7 N4.7\text{ N}4.7 N
9.9 N9.9\text{ N}9.9 N
12.2 N12.2\text{ N}12.2 N
24.0 N24.0\text{ N}24.0 N