A basketball player makes a jump shot. The 0.650-kg ball is released at a height of 1.80 m above the floor with a speed of 7.80 m/s. The ball goes through the net 3.10 m above the floor at a speed of 4.40 m/s. What is the work done on the ball by air resistance, a non-conservative force?

I got -5.199 J, am I correct? Also, is work a vector or scaler, do I keep it as positive or negative?

work is energy is a scalar

Wair = initial K.E. - final K.E. - m g h

positive ... you are correct