Physics :Compressional Stress

The total cross-sectional area of the load-bearing calcified portion of the two forearm bones (radius and ulna) is approximately 2.6 cm2. During a car crash, the forearm is slammed against the dashboard. The arm comes to rest from an initial speed of 80 km/h in 4.9 ms. 

If the arm has an effective mass of 3.0 kg, what is the compressional stress that the arm withstands during the crash?