Extracted text: 1. INTERVISIBILITY OF STATIONS. It is desired to sight form Dimasalang Hill (elev. 196.85m) to Humanon Hill (elev. = 198.15m) 40km away. Sikatuna Hill (elev. = 197.65m), 2.2km away, apparently obstructs the line of sight. If towers of equal height on Dimasalang Gill ang Humabon Hill are to be constructed so that the line just clears Sikatuna Hill by 3.50m, what will be the height of these towers? How high a tower would be required on Humabon Hill alone? On Dimasalang Hill alone?