How does adding mass to the counterweight of a trebuchet affect the amount of work done to launch the projectile?

As the force exerted on the projectile is equal to the mass of the counterweight times the gravitational constant, when the mass is increased, the force will also increase.

Explanation: I hope this helps

This is due to the fact that there will be no air resistance on the projectile allowing 45 degrees to be the perfect arc for maximum distance.