Read the passage given below and solve the questions based on it.
Mr Bose can do a job in two days if his four secretaries A, B, C and D are all present. His efficiency got reduced to respectively as A, B, C and D remain absent. In any day only one secretary remains absent. Also Mr Bose finishes his work exactly in integral number of days.
If each secretary remained absent for at least one day, then in how many days will Mr Bose finish the work?