Let h and k be the lengths of two of the altitudes of triangle ABC, with h =/= k.

Determine, in terms of h and k, upper and lower bounds for the length of the third altitude of triangle ABC.

My first approach to this was to find the area of the triangle, but I do not think that is possible to reach this solution. I do not understand this quesion completeley, can anyone reassure me that I am given two altitudes and I have to find the third one? What is a "bound"?