At 400 K oxalic acid decomposes according to the reaction:
H2C2O4(g)?CO2(g)+HCOOH(g)
In three separate experiments, the intial pressure of oxalic acid and final total pressure after 20,000 s is measured.

Experiment

1
2
3

P H2C2O4 at t = 0
65.8
92.1
111

PTotal at t = 20,000 s

107

150

181

Find the rate law of the reaction.