reason, redolent, incumbent, and detergent

Her room, and it was her room, was redolent of hyacinth. George assumed it was because Martha was a part-time gardener.
“No,” she said, “it’s the detergent.”
“My mistake,” he said.
“And with good reason,” she countered.
“What do you mean?”
“It’s incumbent upon you to read Men Are from Mars, Women Are from Venus. I swear by it.”
“Will I become a better person after having skimmed through it?” He was a speed reader.
“Well,” she said, “let’s talk about it over dinner. By the way, where are you taking me?”