<｜begin▁of▁sentence｜>### Instruction:
As a chemical engineer tasked with optimizing the flow of materials through a network of interconnected reactors, you've modeled your system as a graph where the nodes represent reactors and the edges represent the pathways for material transfer, with the edge weights symbolizing the cost or benefit of transferring materials between reactors. You're given data for your network as follows: reactants flow from 'A' to 'B' at a cost of 2 units, from 'C' to 'D' at a cost of 3 units, from 'D' to 'C' with a benefit of 5 units, from 'B' to 'C' at a cost of 1 unit, and finally from 'C' back to 'A' with a benefit of 8 units. In chemical engineering terms, to ensure the sustainability and efficiency of this system, could you tell if there's a series of reactions leading to a situation where the continuous recycling of materials through these reactors results in an overall decrease in operational costs, effectively a negative cost cycle?
### Response:
import networkx as nx

# Create a directed graph
G = nx.DiGraph()

# Add edges with weights
e = [('A', 'B', 2), ('C', 'D', 3), ('D', 'C', -5), ('B', 'C', 1), ('C', 'A', -8)]
G.add_weighted_edges_from(e)

# Check for existence of negative edge cycle
has_cycle = nx.negative_edge_cycle(G)
print('Graph has a negative edge cycle:', has_cycle)
<|EOT|>
