题目

I was born in a town called Blackburn, in the northwest of England, and lived there till I left home   61  the age of eighteen. My parents had moved to England from India during    62   1970s.As a child, I went to my local school and, of course   63   (speak) English with a local accent. But home was very different: we lived in a kind of “little India”, with a huge extended family of uncles and aunts. I remember   64   (feel) part of this big thing called “family”, and an even   65  (big) thing called “India”. I suppose my family   66(real) influenced me 如图，为保护河上古桥OA，规划建一座新桥BC，同时设立一个圆形保护区．规划要求：新桥BC与河岸AB垂直；保护区的边界为圆心M在线段OA上并与BC相切的圆，且古桥两端O和A到该圆上任意一点的距离均不少于80m．经测量，点A位于点O正北方向60m处，点C位于点O正东方向170m处（OC为河岸），．以所在直线为轴，以所在直线为轴建立平面直角坐标系.（Ⅰ）求所在直线的方程及新桥BC的长；（Ⅱ）当OM多长时，圆形保护区的面积最大？并求此时圆的方程.