The magnetic field lines of a current-carrying circular loop form concentric circles around the wire. At the center of the loop, the lines are nearly straight and perpendicular to the plane of the loop. The direction of the field can be determined using the right-hand thumb rule. 
The direction of the force acting on the electron entering perpendicular to the magnetic field as shown in the figure, will be:
Find the unknown frequency if 24 is the median of the following frequency distribution:
\[\begin{array}{|c|c|c|c|c|c|} \hline \text{Class-interval} & 0-10 & 10-20 & 20-30 & 30-40 & 40-50 \\ \hline \text{Frequency} & 5 & 25 & 25 & \text{$p$} & 7 \\ \hline \end{array}\]