A Scientist Conducts an Experiment to Determine the Rate of the Following

A scientist conducts an experiment to determine the rate of the following reaction: 2 N₂(g) +O₂(g) $\rightarrow$ 2 N₂O(g)
If the initial concentration of N₂ was 0.400 M and the concentration of N₂ was 0.350 M after 0.100 s, what is the average rate of reaction over the first 100 milliseconds?

A) 0.25 M/s
B) 0.50 M/s
C) 1.0 M/s
D) 5.0 M/s
E) 10.M/s