1. The problem statement, all variables and given/known data 1)How many bitstring of length 11 contain three more 0's than 1's? 2)How many string of 5 lowercase letters from the Latin alphabet contain: a) the letter c? b) the letters c and d? c) the letters c and d in consecutive positions with c preceding d and all letters distinct? d) the letters c and d, when c is somewhere to the left of d in the string and all letters are distinct? 3. The attempt at a solution For 1) I got 11C4 2a) I got 26^5 - 25^5 b) 26^5 - 24^5 c) 4C1*2!*24*23*22/2!... I am not sure at all about this one, my logic is that I take away c and d from the sample size, then divide by 2! to get the arrangement where c is infront of d. d) 5C2*2*1*24*23*22/2! I am not sure about this one either, I am basically choosing two positions for c and d, subtracting 2 from 26, then multiplying 2*1 to choose from the c and d, then randomly choosing letters for the remaining spots, then dividing by 2! to get the arrangement where c is to the left of d. Can you guys point out which ones are right and which ones are wrong? Thank you so much.