Enzymes: explain question

A newly discovered bacterium, Pseudomonas plasticivorans, secretes an extracellular enzyme called PETase. PETase is a globular protein that catalyses the hydrolysis of the synthetic polymer PET (polyethylene terephthalate) into its monomers. The reaction occurs outside the bacterial cell. Explain how the lock-and-key hypothesis and the induced-fit hypothesis differ in their description of the binding of PETase to its substrate PET. In your answer, also outline how a colorimeter could be used to investigate the rate of disappearance of PET in this reaction.