Read each sentence to find out whether there is any grammatical error in it. The error, if any, will be in one part of the sentence. Mark the part with the error as your answer. If there is no error, mark ‘No error’ as your answer (Ignore the errors of punctuation, if any).
After several rounds of trial and error, (1)/ the researchers found they could (2)/ maximise percarbamide produce by (3)/ holding the concentration of urea between 15% and 38%. (4)/ no error (5)