Explanation:

According to CFA Institute Standard VI(C) - Referral Fees, members must disclose to clients and prospective clients:

1. The existence of any referral fee arrangement
2. The nature of the arrangement
3. The dollar amount or estimated dollar value of the referral fee
4. The timing of the disclosure must be before the client enters into an agreement

Analysis of Jacobs' actions:

• Jacobs disclosed the arrangement before signing service agreements ✓
• However, he did not provide the estimated dollar value ✗
• Violation: Failure to provide estimated dollar value

Analysis of Amari's actions:

• Amari provided complete details including estimated dollar value ✓
• However, she disclosed after the service agreements were signed ✗
• Violation: Failure to disclose before entering into agreement

Conclusion: Both Jacobs and Amari violated Standard VI(C) - Referral Fees, but for different reasons:

• Jacobs violated by not providing estimated dollar value
• Amari violated by disclosing after the agreement was signed

Therefore, both have violated the Standards.