what is the mathematical relationship between the committed information rate (CIR), committed burst

For the following items,what is the mathematical relationship between the committed information rate (CIR), committed burst (Bc), and committed rate measurement interval (Tc)?

A.
CIR = TC / Bc

B.
CIR = Be / Tc

C.
Tc = CIR / Bc

D.
Tc = Bc / CIR