I need help step by step explanation im not understanding

Project	NPV	Internal Engineers	Additional Costs
1	400000	12	180000
2	570000	4	400000
3	550000	7	70000
4	340000	8	130000
5	725000	10	200000
6	650000	8	225000
7	600000	9	196000

Riesemberg Medical Devices is allocating next year's budget among its divisions. As a result, the R&D Division needs to determine which R&D projects to fund. Each project requires various software and hardware and consulting expenses, along with internal human resources. A budget allocation of $1,300,000 has been approved, and 35 engineers are available to work on the projects. The R&D group has determined that at most one of projects 2 and 7 should be pursued, and that if project 1 is chosen, then project 2 must also be chosen. Develop a model to select the best projects within the budget Click the icon to view the project expected return (NPV), resources, and cost data. Which combination of projects maximizes NPV within the budget? Select all that apply. A. 5 B. 3 c. 7 D. 2 DE. 4 OF. G. 6