code: def EXP_gas(self, base, exponent):
          
          EXP_SUPPLEMENTAL_GAS = 10   # cost of EXP exponent per byte
  
          def nbytes(e):
              result = 0
              for i in range(32):
                  result = Operators.ITEBV(512, Operators.EXTRACT(e, i * 8, 8) != 0, i + 1, result)
              return result
          return EXP_SUPPLEMENTAL_GAS * nbytes(exponent)
docs: Calculate extra gas fee