1. Manpower
   1. Cause 1
   2. Cause 2
2. Machinery
   1. Cause 1
   2. Cause 2
3. Materials
   1. Cause 1
   2. Cause 2
4. Methods
   1. Cause 1
   2. Cause 2
5. Mother nature
   1. Cause 1
   2. Cause 2
6. Mesurement
   1. Cause 1
   2. Cause 2