Calculating Reaction Order with an Excess of One Reactant

A+B -> C+D

The complete data is as follows:

The initial concentration of A is 400 mmol/L and initial concentration of B is 0.4 mmol/L.

The following data is for concentration of C in mmol/L at different times T in seconds

T sec: 0      120   240   360   Infinity
[C]   : 0       0.2   0.3    0.35     0.4

Assuming that the rate law is second order with respect to A (but undetermined wtih respect to B).
Use above data to:
1) write the overall rate equation
2) calculate the rate constant.