Final answer:
The efficient amount of rubber will be recycled when the government creates a B) subsidy of more than $2.00 per tonne of rubber.
Step-by-step explanation:
The efficient amount of rubber will be recycled when the government creates a subsidy of more than $2.00 per tonne of rubber. This is because the external benefit of recycling rubber is $2.00 per tonne, and a subsidy of more than $2.00 would incentivize recycling by covering the cost of recycling and providing an additional benefit.
Any subsidy less than $2.00 would not fully cover the external benefit and would not lead to the efficient amount of recycling.