option valuation, option-pricing model, Black-Scholes Model, Black-Scholes-Merton Model, Robert Brown, Brownian Motion, random walk, stochastics, stochastic process, Bachelier, probability theory, stochasticv theory, Kiyoshi Ito, Ito Calculus, Stochastic Calculus, Continuous Time Finance, Robert Merton, Black-Scholes Value, tick, uptick., downtick, price jump, lognormal distribution, model assumptions, transaction costs,