Given the task definition and input, reply with output. In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.

Question: How long had M.E. Hadfield and Son been a going concern for when Frederick Mappin hired them to build a new house? Passage:Thornbury was built between 1864 and 1865, when Frederick Mappin, the cutlery and steel magnate, commissioned the architects M.E. Hadfield and Son to design a new house for him. Mappin had previously been Master Cutler in 1855 and would go on to become Mayor of Sheffield in 1877/8 and a Liberal MP in 1880. Thornbury is a big bold stone house with curving two storey bay windows. It is in the Classical style with two wings, balustraded parapet and a steep pitched roof with tall chimneys and gables. The main entrance is at the western side of the building and this has a two storey porch and a large oriel window. The house which sits on six acres of land looks over mature gardens which were designed by Robert Marnock. The entrance is reached by a long sweeping drive off Fulwood Road; a small lodge is situated at the entrance to the drive.
Links: a. Sir Frederick Mappin, 1st Baronet b. Classical architecture c. Parapet d. Matthew Ellison Hadfield
d