I'm really confused on this problem[GVIDEO][/GVIDEO]

A company wishes to run a utility cable from point A on the shore to an installation at point B on the island. The island is 6 miles from the shore (point O) It costs $3000 per mile to run the cable on land and $5000 per mile underwater. Assume that the cable starts at A and runs along the shoreline, then angles and runs underwater to the island. Let x represent the distance from O at which the underwater portion of the cable begins, and the distance between A and O be 9 miles.

1. Write the total cost C as a function of x.

2.Find the point at which the line should begin to angle in order to minimize the total cost.

3. what is the minimum cost?