The work done in holding a 30kg of bricks to a height of 20m is

The work done to "HOLD" a load of bricks at any height is zero.
Work is done only when force acts through a DISTANCE.

The work done to LIFT 30 kg of anything to 20m higher than
it already is, is

(force) · (vertical distance)

= (mass) · (gravity) · (vertical distance)

= (30 kg) · (9.8 m/s²) · (20 m)

= 5,880 joules