Unit-ship:Ballista Ship

__NOWYSIWYG__

Description
This ship contains a ballista, which was originally meant for firing grappling hooks. However, the ballista is also very valuable as a precise long-range combat weapon, as it hits the enemy under the waterline, even though it does not cause a large amount of damage. __NOWYSIWYG__


 * During sea battle, the Ballista Ships deploy to the long-range battle line.
 * Ballista Ships fill a battlefield space.

Construction times
$$Construction \ time \ = \left \lceil Base \ time \times 0.95 ^ {n - n_0} \right \rceil$$
 * where :
 * Construction time : The calculated time (in seconds) needed to construct the specific ship on the nth Shipyard's level.
 * Base time : The time (in senonds) needed to construct the specific ship on the Shipyard's first level that the specific ship can be constructed [ for this ship 50 minutes = 3000 seconds ].
 * n : The nth Shipyard's level.
 * n0 : The Shipyard's first level where the specific ship can be constructed [ for this ship is the  Level ].

1 - 10 = 11 - 20 = 21 - 30 = 31 - 38 =