The Following Reaction Was Carried Out:
Ni(CO)₄ + PPh₃(g) $\rightarrow$ PPh₃Ni(CO)₃ + CO
Over 200 Seconds, the Concentration of Ni(CO)4

The following reaction was carried out:
Ni(CO) ₄ + PPh₃(g) $\rightarrow$ PPh₃Ni(CO) ₃ + CO
Over 200 seconds, the concentration of Ni(CO) 4 dropped from 10 M to 2.5 M. What is the average rate of the reaction in M/s over this time period?

A) -0.038 M/s
B) 0.050 M/s
C) -0.050 M/s
D) 1.5 x 10³ M/s
E) 0.038 M/s