ewce09.azraftaohid.me/L4T1/EWCE 464/PracticeForMidQuiz/T6-Data/Exercise1/Readme.txt

How to enable 3D Analyst:

In ArcCatalog and in ArcMap, click the Customize menu. 
Click Extensions and check 3D Analyst. 
Click Close. 

You will need to enable the 3D Analyst in both
ArcMap and ArcCatalog.