Find what is the next letter. Please try to find. O,T,T,F,F,S,S,E,N,_ What is that letter?

P, Q, R, S and T are playing a game of cards. P says to Q, "If you give me six cards, you will have as many cards as T has and if I give you three cards, you will have as many cards as S has." P and Q together have 20 cards more than what S and T together have. If Q has two cards more than what R has and the total number of cards be 133, how many cards does Q have?

Certain number of girls made a plan for one day trip. Their budget to spend on snacks was Rs. 192. But, one of them did not turn up for the trip. Because of this, the remaining girls had to contribute Rs. 8 each in extra. Find out the number of girls who went for the trip.