This is the question:

A triathalon runner racing at sea level begins to grimly scale a hill with an angle of elevation of 9 degree. At the beginning of the hill she passes a 30 km marker and at the top of the hill she passes the 32 km marker. How high is the hill to the nearest metre?

the answer is 0.313 km.

It sounds easy but I can't solve it.Please help.Thank you.