An airplane crosses the Atlantic Ocean 3000 miles with an airspeed of 600 mph. The cost C and dollars per passenger is given by C of X equaling 125 + X / 25 + 33,000 / X, where X is the ground speed, airspeed, plus or minus wind. And it's plus or minus because it depends on if it's a headwind or a tailwind. So part A says what's the cost per passenger for no wind? Well, if there's no wind, that means that the ground speed is just 600 ± 0 because there was no wind. So literally we're just going to figure out what C of 600 is. So 125 plus 600 / 25 + 33,000 / 600. When we plug that into our calculators, we would get 204. Part B says what's the cost per passenger with a headwind of 50 mph? If it's a headwind, it's pushing on the plane or it's taking us slower, it's going against us. So instead of a ground speed of 600, we're going to now have 600 minus the 50 because it's slowing us down. So now we want C of 550, and literally we just stick 550 in everywhere we see our X and we compute the value for the next part. It talks about tailwind of 100. If it's a tailwind, it's coming at the back of us, so it's pushing the plane faster. So we'd have 600 + 100 and we would compute what C of 700 is for the last part. What's the cost per passenger with a headwind? Well, headwind means it's going slower, it's going against us, so we would figure out what CF 500 is.