Coordinate Geometry: JEE Main 2007 Mathematics question

Let A $\left( {h,k} \right)$, B$\left( {1,1} \right)$ and C $(2, 1)$ be the vertices of a right angled triangle with AC as its hypotenuse. If the area of the triangle is $1$ square unit, then the set of values which $'k'$ can take is given by :