$($a$)$ The ciphertext string

RFCTEKTWEXFREQTQ

was produced using a shift cipher over the $27-$letter alphabet

$A=0,B=1,$dots,$Z=25,$lrcorner$=26,$

where the final character $$ indicates a space.

By conducting a frequency analysis of a larger sample of ciphertexts, it has

been found that the plaintext symbol $$ corresponds to the ciphertext sym$-$

bol E$.$ Determine the first word of the plaintext string corresponding to the

ciphertext string given above.

$[5$ marks$]$