1.23 root h1 + 1.23 root h2 = max range
h1 = height of VOR station
h2 = height of a/c
1.23 root 100 + 1.23 root 10000 = 12.3 + 123 = 135.3
If only Flight level is given and height of station = 0 then use 12 root FL i.e. 12 root 100 (if in the above question h1 = 0)