Answer
The magnitude of the force exerted by the father is $~~72~N$
Work Step by Step
The force exerted by the father is equal in magnitude to the horizontal component of the tension.
We can find the magnitude of the force exerted by the father:
$F = F_T~sin~\theta$
$F = (280~N)~sin~15^{\circ}$
$F = 72~N$
The magnitude of the force exerted by the father is $~~72~N$
