The conditions suggested in the question give you
two equations which you can solve to find 
<math xmlns="http://www.w3.org/1998/Math/MathML">
<mrow><mi>p</mi>'</mrow></math>
and 
<math xmlns="http://www.w3.org/1998/Math/MathML">
<mrow><mi>q</mi>'</mrow></math>. Use the same formulation to give

<math xmlns="http://www.w3.org/1998/Math/MathML">
<mrow><mo stretchy="false">(</mo><mi>p</mi>''<mo>,</mo><mi>q</mi>''<mo stretchy="false">)</mo></mrow></math>.

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