Explanation
According to the PMI Professional in Business Analysis objectives and content, the business analyst should recommend the option with the highest functionality score and the lowest cost score. In this case, option A, 1, Custom solution, has the highest functionality score of 10 and the lowest cost score of 1. Therefore, it should be recommended. References:
PMI Professional in Business Analysis objectives and content: PMI-PBA Certification PMI Professional in Business Analysis reference list: PBA Reference List PMI Professional in Business Analysis study guide: PMI.com

Explanation
According to the PMI Guide to Business Analysis, a Pareto analysis is a tool that helps to prioritize problems or causes based on their frequency or impact. It is based on the Pareto principle, which states that 80% of the effects come from 20% of the causes. A Pareto analysis can help to identify the high-priority changes needed to improve a service by showing which problems or causes account for most of the complaints or dissatisfaction. A work breakdown structure analysis, a flowchart, and a cause-and-effect diagram are other tools that can help to analyze a service, but they do not necessarily help to prioritize the changes needed to improve it. References: PMI Guide to Business Analysis, page 145-146.

Explanation/Reference:

Internal rate of return (IRR) is a technique that calculates the annualized rate of return of an investment or a project. IRR can help the business analyst to determine the estimated growth rate of potential solution options by comparing the present value of the expected cash inflows and outflows of each option. IRR can also help to select the option that has the highest rate of return and exceeds the minimum required rate of return or the cost of capital. References: = PMI Professional in Business Analysis (PMI-PBA)Examination Content Outline (2019), page 11; Business Analysis for Practitioners: A Practice Guide (2015), page 66.