The girth seam of a boiler 1.5 m in diameter is a double-riveted lap joint. The rivet pitch is 80 mm, the rivet-hole diameter is 17.5 mm and the plate is 12 mm thick. With allowable stresses of 60 MPa in shear, 130 MPa in bearing and 80 MPa in tension, find the strength of one repeating section (kN), the joint efficiency (%) and the maximum internal pressure (MPa).