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Question

Difficulty: HardSorting and Multi-Column Ordering

The table below presents performance and operational metrics for 8 regional microgrid energy storage facilities.

FacilityTechnologyStorage Capacity (MWh)Round-Trip Efficiency (%)Maintenance Cost ($/MWh)
M-1Solar+Storage4588.514.20
M-2Hybrid6091.016.50
M-3Wind+Storage5088.512.80
M-4Hybrid4091.015.10
M-5Solar+Storage5592.013.80
M-6Hybrid7089.518.00
M-7Wind+Storage6593.511.50
M-8Solar+Storage3588.515.00

Suppose the table is sorted according to the following sequential rules:
1. Primary sort: Technology in ascending alphabetical order.
2. Secondary sort (tie-breaker for identical Technology): Round-Trip Efficiency in descending order (highest to lowest).
3. Tertiary sort (tie-breaker for identical Technology and Round-Trip Efficiency): Maintenance Cost in ascending order (lowest to highest).

After applying this multi-column ordering, what is the Storage Capacity (in MWh) of the facility ranked 5th from the top?

  1. A
    35
  2. B
    40
  3. 45Answer
  4. D
    55
  5. E
    70

Answer

45 MWh
To determine the 5th ranked facility, we follow the three-tier sorting hierarchy: first by Technology (alphabetical), then by Round-Trip Efficiency (descending), and finally by Maintenance Cost (ascending). Sorting by Technology creates three groups: Hybrid (ranks 1–3), Solar+Storage (ranks 4–6), and Wind+Storage (ranks 7–8). Within the Solar+Storage group, the highest efficiency is facility M-5 (92.0%), making it rank 4. Facilities M-1 and M-8 both have 88.5% efficiency. Applying the tertiary rule (lower maintenance cost first), facility M-1 (14.20)precedesfacilityM−8(14.20) precedes facility M-8 ( 15.00). Thus, facility M-1 occupies rank 5. Looking across facility M-1's row, its Storage Capacity is 45 MWh.

Step-by-Step Solution

1
Group and sort facilities by the primary criterion: Technology in alphabetical order.
Group 1: Hybrid (M-2, M-4, M-6); Group 2: Solar+Storage (M-1, M-5, M-8); Group 3: Wind+Storage (M-3, M-7).
Alphabetical order places 'Hybrid' first, followed by 'Solar+Storage', and then 'Wind+Storage'.
2
Sort the 'Hybrid' group (Ranks 1 to 3) using secondary (Efficiency desc) and tertiary (Cost asc) rules.
M-4 and M-2 tie at 91.0% Efficiency; M-4 has lower cost (15.10vs15.10 vs 16.50), placing M-4 1st and M-2 2nd. M-6 (89.5%) is 3rd.
Secondary sort prioritizes higher efficiency, and tertiary sort resolves ties by choosing lower maintenance cost.
3
Sort the 'Solar+Storage' group (Ranks 4 to 6) using secondary and tertiary rules.
M-5 has highest efficiency (92.0%) -> Rank 4. M-1 and M-8 tie at 88.5% Efficiency; M-1 has lower cost (14.20vs14.20 vs 15.00) -> Rank 5: M-1, Rank 6: M-8.
M-1 takes Rank 5 because its 14.20/MWhmaintenancecostbeatsM−8′s14.20/MWh maintenance cost beats M-8's 15.00/MWh cost in the tertiary tie-breaker.
4
Identify the facility in Rank 5 and read its Storage Capacity.
Rank 5 is facility M-1, which has a Storage Capacity of 45 MWh.
Evaluating the 5th entry of the ordered list directly answers the question stem.

Key Concept

Multi-column hierarchical table sorting with primary, secondary, and tertiary tie-breaking conditions.
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Topics

Sorting and Multi-Column Ordering

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