No$,$ the scheme does not have CPA security either.

Distinguisher $($identical to CPA$$)$: The same distinguisher from $($a$)$ can be used to attack CPA security as well. The distinguisher can query the encryption oracle for any message and check for divisibility by $10$ to learn information about the encrypted message.

Advantage: The distinguisher's advantage remains significantly greater than $0.$

If c is divisible by $10,$ it implies the padding scheme successfully created a prime number with a trailing zero. This has a non$-$negligible probability of occurring, especially for smaller message lengths.

If c is not divisible by $10,$ it means the padding scheme failed to produce a prime number with a trailing zero, suggesting a different message was encrypted.

Key Point:

The fundamental flaw lies in the predictability of the padding scheme. Knowledge of the padding scheme's structure allows an attacker to glean information about the message by examining ciphertext properties $($divisibility by $10$ in this case$).$

$1$st step:

The encryption scheme is not CPA secure because an attacker can determine if a message is encrypted by checking if the ciphertext is divisible by $10.$ This is because the padding scheme always adds a trailing zero to the message before encrypting it$.$ If the ciphertext is divisible by $10,$ then the attacker knows that the message was encrypted with the padding scheme. Otherwise, the attacker knows that the message was encrypted with a different scheme.