How do I find the height of a triangle

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%.

I’m stuck on this equation, anyone got the answer?

Which of the following represents the length of a diagonal of this trapezoid?