设函数f(x)=(x2-10x+c1)(x2-10x+c2)(x2-10x+c3)(x2-10x+c4)(x2-10x+c5),设集合M={x|f(x)=0}={x1,x2,...,x9}?N+,
设c1≥c2≥c3≥c4≥c5 ,则c1-c5为( )