Vivek and Rishabh just become friend with Suchita , and they want to know when her birthday is Suchita gives them a list of $10$ possible options?
$May \ 15 \quad May \ 16 \quad May \ 19$
$June \ 17 \quad June \ 18$
$July \ 14 \quad July \ 16$
$August \ 14 \quad August \ 15 \quad August \ 17$
Suchita then tells Vivek and Rishabh separately the month and the day of her birthday respectively
Vivek : I don't know when Suchita's birthday is, but I know that Rishabh does not know too.
Rishabh: At first Ididn't know when Suchita's birthday is, but i know now.
Vivek: Then I also know when Suchita's birthday is.
So when is Suchita's birthday?
(A). $May \ 16$
(B). $June \ 17$
(C). $July \ 16$
(D). Data insufficient
How to solve? The answer is C, but how?
