A large tree in Lisa's backyard will likely fall and cause damage to her home if there is a severe storm. Lisa calls a contractor and says "I will pay you $$500$ if you cut down a damaged tree in my backyard by $9$ PM tomorrow evening." The contractor does not cut down the tree by $9$ PM$,$ and it falls on Lisa's house causing $$5000$ worth of damage. Which of the following is true?

a$.$ Lisa can recover the damages to her house from the contractor because the contractor's silence indicated acceptance of the contract.

b$.$ If this contract is considered a unilateral contract, then the contractor cannot be held responsible for the damage to Lisa's house.

c$.$ If Lisa's offer was to enter into a bilateral contract for tree cutting services, Lisa can recover the damages because the contractor did not respond in timely fashion.

d$.$ Lisa cannot recover any amount because her offer was not reasonably definite.