A pile of steel pipes is stacked in a trapezoidal shape. It is known that there are 5 steel pipes in the uppermost layer and 14 steel pipes in the lowest layer. The difference between two adjacent layers is 1 steel pipe. How many steel pipes are there in this pile?
一堆钢管，堆成近似梯形，已知最上层5根，最下层有14根，相邻两层之间相差1根，这堆钢管共有多少根．
<result>85</result>