The sum of the forces in the vertical direction must be zero, so we have:
$$F + 4 \text{ kN} + 6 \text{ kN} + 9 \text{ kN} + 6 \text{ kN} = 0$$
Solving for F, we get:
$$F = -25 \text{ kN}$$
This means that the force F is acting downwards, which is consistent with
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