如图所示对接式螺栓连接，主板厚l₁=10mm，盖板厚l₂=6mm，板宽均为<img src="https://nimg.ppkao.com/2019-04/xiaotian/2019041116152220083.jpg?sign=4987d247d8ab415ee60258888972b0bc&t=62d5c3ca" />=250mm，已知螺栓直径d=20mm，许用剪应力<img src="https://nimg.ppkao.com/2019-04/xiaotian/2019041116153367801.jpg?sign=7cf359f505f2df936fd557753bc45eaf&t=62d5c3ca" />=130MPa，设用挤压应力<img src="https://nimg.ppkao.com/2019-04/xiaotian/2019041116155378612.jpg?sign=40f43675cb90e1c4eb35688ddc294b69&t=62d5c3ca" />=300MPa，钢板的许用拉应力<img src="https://nimg.ppkao.com/2019-04/xiaotian/2019041116160142421.jpg?sign=a55c7873ccb59fe2ab9b8ec4c4194063&t=62d5c3ca" />=170MPa，承受轴向拉力P=300kN，螺栓排列每列最多为二个，则该连接每边所需要的螺栓个数最少为（）<br /> <img src="https://nimg.ppkao.com/2019-04/xiaotian/2019041116161040781.jpg?sign=a89305be6f760c5aaa7a5c50e9ee4bd0&t=62d5c3ca" />&ensp;&ensp;