Elimination Half-life from a graph

The lecturer gave us a little exercise to better understand elimination half-life but I am still very confused about what I should do.

So I have administrated 600mg of drug X which comes in 2 formulations, A and B. Formulation A is represented by the solid line and Formation B by the dash line in the attachment below.
I have to determine the elimination half-life and clearance for drug X by looking at the graph. The lecturer told me that they are the same for both formulations, but how can that be possible if the graphs look different?