To find the molarity of the trimethylamine solution, we first need to calculate the hydroxide ion concentration in the solution using the pH.

Since pH = 11.12, the hydroxide ion concentration can be calculated using the formula:
pOH = 14 - pH
pOH = 14 - 11.12
pOH = 2.88

Now, the hydroxide ion concentration can be calculated using the relationship between pH, pOH and the concentration of hydrogen ions and hydroxide ions in water:
[H+] = [OH-] = 10^(-pOH)
[OH-] = 10^(-2.88)
[OH-] = 1.59 x 10^(-3) M

Since (CH3)3N is a weak base that reacts with water to form hydroxide ions, we can assume that all of the trimethylamine will react to form hydroxide ions, allowing us to calculate the initial concentration of trimethylamine (CH3)3N:

Kb = [OH-][CH3)3N] / [(CH3)3NH+]
6.3 x 10^-5 = (1.59 x 10^-3)(x) / (x)
x = 0.0397 M

Therefore, the molarity of the aqueous solution of trimethylamine is 0.0397 M.