Permutaions&combinations3

A group of friends are going to choose 10 songs from the top 50 hit songs, and imput them into the playing list according to the playing sequence.

Song A,B,C are their favourite songs among the top 50 songs.

(a) If A,B,C are input to the first, second and third places respectively in the playing list, how many different playing lists can be formed?

(b) If A,B,C are input to the first 3 places in the playing list, how mant different playing lists can be formed?

(c) If A,B,C are imput to the playing list, how many different playing lists can be formed?

(Express your answers in scientific notation, and correct to 3 sig. fig.)