A first order chemical reaction has a rate constant of 8.7×103 s-1 at 30 °C and a rate constant of 5.8×104 s-1 at 64 °C.

Calculate the activation energy, Ea, for the reaction.

I keep getting 5.25e-6 kJ/mol but apparently that's not the correct answer.
ln(5.8e4/8.7e3)=-ea/8.315e-3(1/337-1/303)

I posted a response to your earlier post. I get 47,369 J using your numbers.