At a certain concentration of reactants the rate of appearance of water in the following reaction is $0\mathrm{.}68$ M$/$s$.$ HINT: Watch the sign of the rate!

$4$NH$3+7$O$24$NO$2+6$H$2$O

$($A$)$ What is the rate of reaction of O$2?$

$0\mathrm{.}793$

Correct: Your answer is correct.

M$/$s

$($B$)$ What is the rate of reaction of NH$3?$

Incorrect: Your answer is incorrect.

M$/$s

$($C$)$ What is the rate of reaction of NO$2?$