0 votes 0 votes I am not getting here that what is a and b are these elements of the set or two subsets of X ? radha gogia asked Oct 10, 2015 radha gogia 1.1k views answer comment Share Follow See 1 comment See all 1 1 comment reply vijaycs commented May 15, 2016 reply Follow Share I think a and b are two subsets of X, because $\subseteq$ represents subset here. If it is elements they they should write like a,b $\epsilon$ X. But even if it is subset then what would be result for following example- If X = { 1, 2, 3, 4, 5, 6, ... } a= {1, 2, 3, 4} and b= { 3, 4, 5, 6} And a $\cap$ b = {3, 4 } So f (3, 4) = ?? 0 votes 0 votes Please log in or register to add a comment.