One of the following does not represent a valid combination of ‘Class’ of insulating material :

One of the following does not represent a valid combination of ‘Class’ of insulating material and its limiting temperature in ‘Degree Centigrade’.

1. ‘Class- H’ – 1800C
2. ‘Class- B’ – 1200C
3. ‘Class- A’ – 1050C
4. ‘Class- F’ – 1550C