Refer to the table.

Let’s calculate the total cost for each solution based on the most likely maximum duration (20 + 10 = 30 months) to ensure conservative, flexible planning.

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DWDM over dark fiber:

CAPEX = $200,000

OPEX (annual): $100,000⇒for 30 months = (2.5 × $100,000) = $250,000

Installation fee = $30,000

Total = $200,000 + $250,000 + $30,000 = $480,000

CWDM over dark fiber:

CAPEX = $150,000

OPEX (annual): $100,000⇒for 30 months = (2.5 × $100,000) = $250,000

Installation fee = $25,000

Total = $150,000 + $250,000 + $25,000 = $425,000

MPLS wires only:

CAPEX = $50,000

OPEX (annual): $180,000⇒for 30 months = (2.5 × $180,000) = $450,000

Installation fee = $5,000

Total = $50,000 + $450,000 + $5,000 = $505,000

Metro Ethernet:

CAPEX = $65,000

OPEX (annual): $100,000⇒for 30 months = (2.5 × $100,000) = $250,000

Installation fee = $5,000

Total = $65,000 + $250,000 + $5,000 = $320,000

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Analysis:

Metro Ethernet has the lowest overall cost at $320,000 and provides sufficient flexibility for workload migration since "all connectivity options meet technical requirements."

Metro Ethernet is typically more flexible than DWDM/CWDM for temporary or dynamic migration projects because it does not require optical expertise or complex dark fiber management.

MPLS is more expensive here and less flexible for large-scale Layer 2 migrations.

CWDM/DWDM are suitable for permanent solutions where long-term investment is justified, but not optimal here due to cost.

Therefore, best ROI and flexibility: Metro Ethernet

Final correct answer: D