Evaluate Heat Device Practice Test

A student builds a hot lunch container to keep soup warm. Design: 2 cm foam walls, a tightly sealed lid, and a reflective interior lining (foil) inside a plastic shell. Construction: foam panels glued to form a box, foil taped to the inner walls, and a rubber gasket added around the lid.

Test results: The soup started at $75^\circ\text{C}$. After 5 hours, the soup temperature was $65^\circ\text{C}$. The container held 500 mL of soup. Total cost of materials was $\$18$.

Criteria for success: (1) Keep food at $\ge 60^\circ\text{C}$ for 5 hours, (2) hold 500 mL, (3) cost $<$20$.

Based on the test data, what is the best overall evaluation of this design?

Two hot lunch container designs are compared.

Design A (basic foam): 2 cm foam walls, sealed lid, no reflective lining. Test: started at $75^\circ\text{C}$ and was $58^\circ\text{C}$ after 4 hours. Cost: $\$12$.

Design B (foam + reflective): 2 cm foam walls, sealed lid, reflective interior lining. Test: started at $75^\circ\text{C}$ and was $64^\circ\text{C}$ after 4 hours. Cost: $$18$.

Criteria: Keep food at $\ge 60^\circ\text{C}$ after 4 hours and cost $<\$20$.

Which evaluation is correct?