A department store purchases logo shirts at a cost of $10 per shirt. They mark up the price 100% and put them on the sales floor. Every month that a shirt doesn’t sell, the store reduces the selling price by 25%. After three monthly markdowns, the final shirt from the shipment is sold. There is a 5% sales tax on the selling price. What is the total cost to the customer?

Aspacecraft can attain a stable orbit 300 kilometers above earth if it reaches a velocity of 7.7 kilometers per second. the formula for a rocket's maximum velocity v in kilometers per second is vequalsminus0.0098tplusc ln upper r, where t is the firing time in seconds, c is the velocity of the exhaust in kilometers per second, and r is the ratio of the mass of the rocket filled with fuel to the mass of the rocket without fuel. find the velocity of a spacecraft whose booster rocket has a mass ratio of 20, an exhaust velocity of 2.1 km/s, and a firing time of 15 s. can the spacecraft achieve a stable orbit 300 km above earth?