A bolted joint has four bolts arranged as shown in figure. The cross sectional area of each bolt is $$25\,m{m^2}.$$. A torque $$T = 200$$ $$N$$-$$m$$ is acting on the joint. Neglecting friction due to clamping force, maximum shear stress in a bolt is ______ $$MPa.$$

A cantilever bracket is bolted to a column using three $$M12 \times 1.75$$ bolts $$P, Q$$ and $$R.$$ The value of maximum shear stress developed in the bolt $$P$$ (in $$MPa$$) is _______________.

A horizontal plate has been joined to a vertical post using four rivets arranged as shown in the figure. The magnitude of the load on the worst loaded rivet (in N) is ___________.

A bolt of major diameter $$12$$ $$mm$$ is required to clamp two steel plates. Cross sectional area of the threaded portion of the bolt is $$84.3$$ $$m{m^2}$$ . The length of the threaded portion in grip is $$30$$ $$mm,$$ while the length of the unthreaded portion in grip is $$8$$ $$mm.$$ Young's modulus of material is $$200$$ $$GPa.$$ The effective stiffness (in $$MN/m$$) of the bolt in the clamped zone is _______.