Complex sentence: THSRC announced on December 28,1999, that it would negotiate a final contract with TSC, and the contract, which included the supply of rolling stock, was signed on December 12,2000.
Split into simpler sentences: THSRC announced on December 28,1999, that it would negotiate a final contract with TSC. The contract, which included the supply of rolling stock, was signed on December 12,2000.