Correction in question no 9 of surveying assignment

A chain was tested before starting the survey, and was found to be exactly 20 meters. At the end of the survey, it was tested again and was found to be 20.12 m. Area of the plan of the field drawn to a scale of 1 cm = 8 m was (50 + x) cm² (where x is the last two digit of your roll number). Find the true area of the field in square meters.