Find the average rate of change over the given interval:
f(x )= 3^x , [1,4]

the choices are:
3
26
78
81

The answer to your question is 12 moles of water.

Step-by-step explanation:

Reaction

                            2 O₂   +   CH₄     ⇒     CO₂    +   2 H₂O

If Oxygen is in excess, then the limiting reactant is methane and we calculate the moles of water produced considering the moles of methane.

                          1 mol of methane  2 moles of water

                           6 moles of methane   x

                           x = (6 x 2) / 1

                           x = 12 moles of water