A load of 144 kN acts on the repeating section of the triple-riveted butt joint in following figure. Length of section is 200 mm, diameter of rivet holes is 23.5 mm thickness of main plate is 14 mm and of each cover plate is 10 mm. 

a) Determine the shearing, bearing, and tensile stresses developed in the joint. 

b) If steel plates are st37 quality and allowable tensile stress is 1.44 t/cm², check the steel plate and bolts are safe or not.