There are 26 letters in the English alphabet. If we separate the group (a, some 10 letters, z), we will be left with 14 more letters. These 15 objects ( 1 group +14 letters) can be arranged among themselves in 15! ways. Since either a or z can be at the beginning or the end of the group of 12 letters (a, some 10 letters, b), the number of possible arrangements of the group will be 2×(1P1×10P10×1P1)=2×10!. Also, each group of 10 letters can be selected from the remaining 24 letters ( except a and b) in 24C10 ways. Required total number of ways =(2×10!×24C10)×15!