Please explain this:

Daniel agreed to build an apartment building for Steven for $1,000,000.Under the liquidated damages clause of the contract, Daniel was to pay $10,000 per day for every day the building was not completed after the completion date stated in the contract.Daniel was 20 days late in finishing the job, losing 10 days to a strike and 10 day because of late delivery of materials.Daniel refuses to agree to have $200,000 deducted from the purchase price.Is the liquidated damages clause in this contract valid and enforceable?