AP EAMCET Engineering 2015 Code C Paper

Word QUESTION has 8 letters
so total number of word can be formed are 8!
For exactly two letters between Q and S
Q_ _S_ _ _ _ , _ Q_ _S_ _ _, _ _ Q_ _S_ _ , _ _ _Q_ _S _, _ _ _ _Q_ _S
And similarly other 5 will be formed by interchanging Q and S
so total favourable outcomes=5*2*6!
Probability =5*2!*6!/8!=5/28