Help needed right away this is timed

Which of the following is the formula for the sequence graphed below

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%.

The distance of a chord from the centre of a circle is 12cm and the lenght of the chord is 10cm. find the radius of the circle