ATP produced during glycolysis is a result of substrate level phosphorylation. Explain.

 
Substrate-level Phosphorylation is a type of metabolic reaction that results in the formation of Adenosine Triphosphate (ATP) or Guanosine Triphosphate (GTP) by the direct transfer and donation of a phosphoryl (PO3) group to Adenosine Diphosphate (ADP) or Guanosine Diphosphate (GDP) from a phosphorylated reactive intermediate.
In glycolysis substrate level phosphorylation occurs in following two reactions

(i) 2 molecules of 1,3 -diphosphoglyceric acid react with 2 molecules of ADP to form 2 molecules of 3 -phosphoglyceric acid and 2 molecules of ATP. 
1,3-diphosphoglycericacid(2molecules)+2ADPMg2+Phosphotransterase2-phosphoglycericacid(2molecules)+2ATP

(ii) 2 molecules of phosphoenolpyruvic acid reacts with 2 molecules of ADP to form 2 molecules of pyruvic acid and 2 ATP.
2-phosphoenolpyruvicacid(2molecules)+2ADPMg2+PyruvickinasePyruvicacid(2molecules)+2ATP