The opposite parties cannot take advantage of their own error. When they accepted his application wherein preferences were given, they could have rejected. They had offered the post of Statistical Investigator Grade-II and he was not having qualified for same, but he was having qualified for the other two posts he had given. Secondly, there is no provision in the rules guiding selection and recruitment of the Railway employees or any stipulation in the advertisement that candidature can be cancelled on the ground that has been reflected in the impugned notice dated 15.03.2013. It is further seen that the applicant could have been selected for any of the two other posts, he opted in his application. However, the petitioner-authorities did not scrutinize his application at the time of calling him for production of the documents regarding educational qualification. If the authorities have acted in bonafide manner, they could have easily found out that the candidate was not having the qualification to be appointed as Statistical Investigator Grade-II. But, he is eligible for the other two posts he had given in his preferences. It was necessary on the part of the SSC to declare the applicant ineligible for the Statistical Investigator Grade-II and he should have been given an opportunity to choice any one of the other two posts he has opted for. Since he is qualified for the other posts he has given preferences, his application cannot be rejected and he cannot be denied the employment.