Work done by a coolie in carrying load on his head is ZERO. This is because the force of gravity acts in vertical downward direction and displacement of load takes place in horizontal direction hence angle between displacement and force becomes 90°.

Since, Work= FS cos θ

Work done in this case is zero because cos 90°=0

Note: Even if there is no work done but the energy of the coolie is still consumed in carrying the luggage.