Analyzing a Titration Curve: Diprotic Acid with Strong Base

The titration curve shown represents the titration of a 0.100 M solution of an unknown acid with 0.100 M NaOH. Based on the two distinct buffer regions and two equivalence points, what type of acid is being titrated?

At approximately what pH does the first equivalence point occur in the titration curve, and what does this indicate about the acid being titrated?

If the volume at the first equivalence point is approximately 15 mL, what is the total number of moles of acid originally present in the solution? Use the formula $n = M_1V_1 = M_2V_2$ where $M_2 = 0.100$ M and $V_2 = 0.015$ L.