Force due to gravity = 4080 x 9.81 = 40,025 N
Force of trailer parallel to slope = 40025 sin 14.5 = 10021 N (resolve horizontally)
I used the acceleration of gravity as 9.81 m/s. If they want you to use 10 m/s, just switch it with the 9.81 in the first equation. Ignore the speed of the trailer. That is just to throw you off.
