The number of degrees of freedom of a planar linkage with 8 links and 9 simple revolute joints is

An instantaneous configuration of a four-bar mechanism, whose plane is horizontal, is shown in the figure below. At this instant, the angular velocity and angular acceleration of link $${Q_2}\,\,A$$ are $$\omega = 8\,\,rad/s$$ and $$\alpha = 0$$, respectively, and the driving torque $$(T)$$ is zero. The link $${Q_2}\,\,A$$ is balanced so that its center of mass falls at $${Q_2}.$$

Which kind of $$4$$-bar mechanism is $${Q_2}AB{O_4}?$$

An instantaneous configuration of a four-bar mechanism, whose plane is horizontal, is shown in the figure below. At this instant, the angular velocity and angular acceleration of link $${Q_2}\,\,A$$ are $$\omega = 8\,\,rad/s$$ and $$\alpha = 0$$, respectively, and the driving torque $$(T)$$ is zero. The link $${Q_2}\,\,A$$ is balanced so that its center of mass falls at $${Q_2}.$$

At the same instant, if the component of the force at joint $$A$$ along $$AB$$ is $$30 N,$$ then the magnitude of the joint reaction at $${Q_2}$$.

An instantaneous configuration of a four-bar mechanism, whose plane is horizontal, is shown in the figure below. At this instant, the angular velocity and angular acceleration of link $${Q_2}\,\,A$$ are $$\omega = 8\,\,rad/s$$ and $$\alpha = 0$$, respectively, and the driving torque $$(T)$$ is zero. The link $${Q_2}\,\,A$$ is balanced so that its center of mass falls at $${Q_2}.$$

At the instant considered, what is the magnitude of the angular velocity of $${O_4}B?$$