Step 1: Note down the direct clues.
Four people, Arvind, Biswajeet, Chinmay and Dhruv, each hold one of four professions, MD, Lawyer, Doctor and Engineer, and each started on one of four salaries, Rs 40,000, Rs 50,000, Rs 60,000 and Rs 70,000.
Two professions are given directly: Biswajeet is the lawyer, and Dhruv is the engineer. That leaves MD and Doctor to be shared between Arvind and Chinmay.
Step 2: Use the did not start on Rs 50,000 clues.
We are told the MD earned the most, so the MD's salary is Rs 70,000, the top value.
We are also told Biswajeet, the lawyer, did not start on Rs 50,000, and Dhruv, the engineer, did not start on Rs 50,000 either.
Since somebody among the four must have started on Rs 50,000, and it cannot be Biswajeet or Dhruv, and it cannot be the MD whose salary is fixed at Rs 70,000, the Rs 50,000 salary must belong to whichever of Arvind or Chinmay is the Doctor, not the MD.
Step 3: Use Arvind earned more than Biswajeet to fix who is MD.
The three remaining salaries, Rs 40,000, Rs 50,000 and Rs 60,000, go to Biswajeet, Dhruv and the Doctor, with the Doctor taking Rs 50,000 as just shown.
We also know the Doctor earned more than Dhruv, so Dhruv's salary must be less than Rs 50,000, which forces Dhruv to Rs 40,000, leaving Biswajeet with Rs 60,000.
Now check Arvind earned more than Biswajeet, who has Rs 60,000. If Arvind were the Doctor, Arvind would earn only Rs 50,000, which is less than Biswajeet's Rs 60,000, breaking this clue. So Arvind cannot be the Doctor, which means Arvind is the MD on Rs 70,000, and Chinmay is the Doctor on Rs 50,000.
Step 4: Check every clue against the full solution.
Arvind, MD, Rs 70,000. Biswajeet, Lawyer, Rs 60,000. Chinmay, Doctor, Rs 50,000. Dhruv, Engineer, Rs 40,000.
Arvind, 70, is more than Biswajeet, 60: holds. Doctor Chinmay, 50, is more than Engineer Dhruv, 40: holds. Biswajeet and Dhruv both avoid Rs 50,000: holds. The MD, Arvind, has the highest salary: holds. Every clue is satisfied, and this is the only arrangement that works.
Final Answer:
Chinmay's profession is Doctor.
\[ \boxed{\text{Doctor}} \]