A child pulls a 10 kg sled on level ground with a horizontal force of 40 N. Friction opposes the motion with 25 N and air resistance with 5 N, both acting opposite to the pull. Which option correctly states the net horizontal force on the sled and whether the forces are balanced or unbalanced?
a) 15N,unbalanced
b) 10N,unbalanced
c) 70N,unbalanced
d) 10N,balanced