Air glider question and air resistance

[BJducky]

Homework Statement

Early test flights for the space shuttle used as a glider (mass of 980kg). After a horizontal launch at 480 km/h at a height of 3500m, the glider eventually landed at a speed of 210 km/h. What would its landing speed have been in the absence of air resistance? also, what was the average force of air resistance exerted on it if it came in at a constant glide angle of 12degrees to the Earth's surface?

I attempted the first question by calculating the vertical component of the velocity and then using the Pythagorean theorem to calculate compound velocity. However, how I am completely at a loss of how to approach the second part. Please help.

 

[Hootenanny]

HINT: What is the work done by air resistance?

 

[BJducky]

So, by using the theta and the given vertical component, I was able to find the total distance. Then, using the initial PE and final KE, I found the difference in energy lost and therefore work done by the air, setting up the equation W=fd I got f(air resistance)=-1897.8N. Does that sound right to you guys?