1.a)Find the number of 4*4 patterns you can make using eight white,four grey,four blue tiles,

my thinking $\displaystyle \frac{16}{8!4!4!}=900,900$

b) How many different 10-digit telephone numbers contain four 2s three 3s and three 7s?

c) A band has recorded five hit singles. In how many different orders could the band play three of these five songs at a concert?