What is the percentage constitution of customer relationships among the total intangible assets subject to amortization?
{"": {"Fair Value": "(U.S. $ in thousands)", "Useful Life": "(years)"}, "Developed technology": {"Fair Value": 35600, "Useful Life": 5}, "Customer relationships": {"Fair Value": 48600, "Useful Life": 10}, "Trade name": {"Fair Value": 3700, "Useful Life": 5}, "Total intangible assets subject to amortization": {"Fair Value": 87900, "Useful Life": ""}}
customer_relationships = df["Customer relationships"]["Fair Value"]
total_intangible_assets_subject_to_amortization = df["Total intangible assets subject to amortization"]["Fair Value"]
answer = customer_relationships / total_intangible_assets_subject_to_amortization * 100.0