′MOTHER′
Rearrange in alphabetic order EHMORT
Number of words start with E=5!
Number of words start with H=5!
Number of words start with ME=4!
Number of words start with MH=4!
Number of words start with MOE=3!
Number of words start with MOH=3!
Number of words start with MOR=3!
Number of words start with MOTE=2!
Number of word MOTHER=1
2×5!+2×4!+3×3!+2!+1=240+48+18+2+1=309