A stock price changes each day either by going up $1 or going down $1 each with probability .

a. What is the probability that the stock price will increase by $10 before decreasing from its present value by $25?

b. What is the expected number of days that will elapse before the stock increases in price $10 or decreased by $25?

c. What is the expected number of days that will elapse before the stock increases by $10 while avoiding a decrease of $25?