When securing a non-cubic boulder with an unstable base, the four surrounding chains must have a WLL of at least _________.

Special Circumstances: Securing a Non-Cubic Shaped Boulder with an Unstable Base
The securement of a non-cubic shaped boulder with an unstable base must meet these requirements in addition to the other large boulder requirements.
- Surround the top of each boulder at a point between 1/2 and 2/3 of its height with one chain.
- The WLL of the chain must be at least 50% of the weight of the boulder.
- Attach four chains to the surrounding chain and the vehicle to form a blocking mechanism that prevents any horizontal movement.
- Each chain must have a WLL of at least 25% the weight of the boulder, and the angle of the chain must be less than 45° from the horizontal.