Final answer:
Under the fair value method, the stock option transaction results in a $90,000 decrease to Kessler's net income for the year ended December 31, 2015, with one-third of the total compensation expense recognized each year over the three-year service period.
Step-by-step explanation:
The impact on Kessler's net income for the year ended December 31, 2015, as a result of the stock option transaction under the fair value method is a $90,000 decrease. This is because the total compensation expense of $270,000 determined by the Black-Scholes option pricing model is recognized over the service period of three years. Therefore, one-third of the total expense, or $90,000, is recognized in 2015, reducing the net income by that amount.