The following chemical reaction: A products shows first order kinetics with respect to A; rate = k[A].

Assume k = 5.06 x 10^-5 s^-1 .

If the concentration of A is 0.212 mol L^-1 at 6.47 hours after the reaction starts, what was the concentration of A (in mol L^-1) when the reaction started?

Remember: if you want to express an answer in scientific notation, use the letter "E". For example "4.32 x 10⁴" should be entered as "4.32E4".