. . .  .¹

Note: the abbreviation C (for Coulombs) can often be distinguished from the symbol C (for capacitance) only by context. Here you can tell them apart by font, but in handwritten solutions this is impractical. In case of ambiguity one can always write out ``Coulombs'' without abbreviation.

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. . . meters.²

The value you calculate will not agree with the value you look up; this is because the r₀ listed in textbooks is actually the Compton radius of the electron and has a completely different meaning. Nevertheless, numerous texts glibly describe r₀ as defined in this problem. The amazing thing is that the two values are so close!

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