Assign $($encode$)$ each letter in the English alphabet a

number between $1$ and $26$ in the standard order as shown

in the table below:

A B C D E F G H I J K L

$123456789101112$

N O P Q R S T U V W X Y

$141516171819202122232425$

Define a product encryption function on the English alphabet that encrypts$/$decrypts each plain text character

m as an encrypted character c as follows:

Encrypt: c $=($key$1$ m$)$ mod $27$

Decrypt: m $=($key$2$ c$)$ mod $27$

Where key$1$

is the public key, key$2$

is the private key, and

key$1$ key$21$ mod $27.$

Suppose it is known that the public key is key$1=4.$

Crack this encryption then decrypt the following strings:

a$.$ Decrypt the string $$XIUU$$:

b$.$ Decrypt the string $$HFFY$$: