A proton (mass 1 u) is shot toward an unknown target nucleus at a speed of 2.50x10^6 m/s. The proton rebounds with its speed reduced by 25% while the target nucleus acquires a speed of 3.37x10^5 m/s.
Part A
What is the mass, in atomic mass units, of the target nucleus? Express your answer as an integer and include the appropriate units.