find the english error and explain it IBM has laid off 20 percent of their workforce with a signature on a single piece of paper

Kalau IBM nya singular maka IBM has, dan their diganti dengan its
IBM has laid off 20 percent of its workforce by signing a signature on a single piece of paper
Kalau IBM nya plural maka menjadi IBM have, dan their dipertahankan 
IBM have laid off 20 percent of their workforce by signing a signature on a single piece of paper