The range of parameter `' a '` for which the variable line `y=2x+a` lies between the circles `x^2+y^2-2x-2y+1=0` and `x^2+y^2-16 x-2y+61=0` without intersecting or touching either circle is `a in (2sqrt(5)-15 ,0)` `a in (-oo,2sqrt(5)-15 ,)` `a in (0,-sqrt(5)-1)` (d) `a in (-sqrt(5)-1,oo)`