What is the role of Euler's Totient function $($

$)$ in RSA?

Select one:

a$.$ It determines the number of positive integers less than a given number that are relatively prime to it$.$

b$.$ It helps choose appropriate public and private exponents for the encryption and decryption process.

c$.$ It provides a way to efficiently compute modulo calculations required for decryption

d$.$ All of the above.