If we use extended Vigenere cipher $(26$ English letters and $10$ decimal digits$)$ to encrypt $$COM$09$ using key word $$Covid$19.$ Then, we obtain $----------------------$ as a ciphertext. Note that Z$=25,0=26,1=27,2=28......$ Hint: Use modular arithmetic.

a$.$

$427$A$3$T$25$

b$.$

E$27$B$3$TZ

c$.$

E$27$A$3$T$0$

d$.$

E$278$D

e$.$

None of these

f$.$

E$27$A$3$T$2$