Time management is very much important in IIT JAM. The eduncle test series for IIT JAM Mathematical Statistics helped me a lot in this portion. I am very thankful to the test series I bought from eduncle.
Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
Chandra prakash
see the link. https://proofwiki.org/wiki/Infinite_Set_has_Countably_Infinite_Subset
dear see attached link