N=pq=221=13×17.
(p-1)(q-1)=12×16=192.
e=5 (encryption exponent).
The decryption exponent is d, such that:
de=1 mod (p-1)(q-1):
5d=1 mod 192.
5d=192m+1,
When m=2, 5d=385, decryption factor d=77; 5×77=1 mod 192.
Plaintext=Cᵈmod N = C⁷⁷ mod 221.
For decrypted Tfg, T=64+20=84, f=96+6=102, g=103.
So C=84⁷⁷ mod 221.
b=84, e=77=115₈=1001101.
The next step is to use modulo exponentiation and to apply d to decrypt each letter.
More to follow...