D, L, M, Z, B and K are six friends, each weighing differently on a weighing scale. M is heavier than only two friends. B is lighter than only D but immediately heavier than K. Z is lighter than M but NOT the lightest. K is heavier than how many friends?

Among five friends Pinky, Pooja, Prachi, Neha, and Payal: Pinky is older than only Pooja. Prachi is older than both Pooja and Pinky. Also, Prachi is younger than Neha, who is not the oldest. Who is the oldest?

Suraj ranked 17th from the bottom and 13th from the top in his class. How many students are there in his class?