Type in a value that represents "as likely as not" in a decimal form. I really need help

Adepartment store purchases screen-printed t-shirts at a cost of $5 per shirt. they mark up the price 150% (making the selling price 250% of the store's purchase price) and put them on the sales floor. every month that a t-shirt doesn't sell, the store reduces the selling price by 25%.

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?

What is the value of the expression i 0 × i 1 × i 2 × i 3 × i 4? 1 –1 i –i