If we use extended Vigenere cipher $(26$ English letters and $10$ decimal digits$)$ to encrypt $$COVID$1$ using key word $2020$AZ$.$ Then, we obtain $----------------------$ as a ciphertext. Note that Z$=25,0=26,1=27,2=28......$ Hint: Use modular arithmetic.

$6$

a$.$

$4$EN$8$DQ

b$.$

$4$EN$7$DQ$1$

c$.$

$4$EN$9$DQ$1$

d$.$

None of these

e$.$

$3$EN$8$DQ$2$