Strangely, the person who increases the original five years to fifteen is the (a) lawyer, (b) banker, (c) judge

The correct answer is (a) the lawyer

One evening a wealthy banker hosts a party at which a discussion of capital punishment begins. While most of the guests disapprove of capital punishment, the banker disagrees with them:

Capital punishment kills a man at once, but life-long imprisonment kills him slowly.

While others consider the death penalty immoral and unsuitable for Christian countries, the young lawyer contends that both the death sentence and the life sentence are immoral,

...but if I had to choose between the death penalty and imprisonment for life, I would certainly choose the second. To live anyhow is better than not at all.

Excited by the discussion, the banker challenges the lawyer's opinion,

"It's not true! I'll bet you two million you wouldn't stay in solitary confinement for five years."
"If you mean that in earnest....I'll take the bet, but I would stay not five, but fifteen years."

"Done!" the banker shouts and the young lawyer resounds, "Agreed!" However, his rash addition of ten years to his confinement becomes a tremendous burden to his soul.
In the first five years, the lawyer is allowed to have a musical instrument, books, and paper and pen on which to write letters. He can also have wine and tobacco, but the lawyer refuses to drink or smoke because wine excites the senses and smoke spoils the air. He suffers terribly from loneliness the first year, but he plays the piano and reads. During the second year, he does not touch the piano, nor does he read. Instead, he drinks wine and eats and lies on his bed indolently. At times he speaks angrily to himself aloud, or he writes all night, then tears up what he has written. Sometimes he cries.

At the end of these five years, the lawyer could have redeemed his spirit if he were only to have kept the bet to this length. But, in a display of bravado, he has sentenced himself to a decade longer, a decade of the deprivation of human contact that destroys his spirit. For, in his impulsive gesture, he has discounted the need in all men for others since it is only in sharing one's laughter, love, thoughts, and feelings that man finds meaning in life.