Step 1: Build an inequality chain from the clues.
Arvind earned more than Biswajeet gives Arvind greater than Biswajeet.
The Doctor earned more than Dhruv gives Doctor greater than Dhruv.
The MD earned the most gives MD greater than everyone else.
Step 2: Place Biswajeet and Dhruv using the not Rs 50,000 clues.
Since Biswajeet, the lawyer, and Dhruv, the engineer, both avoid Rs 50,000, and the MD already owns the top value Rs 70,000, the value Rs 50,000 has to fall on the Doctor. That leaves only Rs 40,000 and Rs 60,000 for Biswajeet and Dhruv.
Because the Doctor on Rs 50,000 earned more than Dhruv, Dhruv cannot be Rs 60,000, since that would make him earn more than the Rs 50,000 Doctor, so Dhruv equals Rs 40,000 and Biswajeet equals Rs 60,000.
Step 3: Use Arvind greater than Biswajeet to finish the chain.
Arvind must earn more than Biswajeet's Rs 60,000, and the only figure left above Rs 60,000 is Rs 70,000. Arvind cannot be the Doctor, since Rs 50,000 is less than Rs 60,000, so Arvind is the MD on Rs 70,000, and Chinmay, the last person, becomes the Doctor on Rs 50,000.
Step 4: Rank all four salaries.
Rs 70,000, Arvind, is greater than Rs 60,000, Biswajeet, which is greater than Rs 50,000, Chinmay, which is greater than Rs 40,000, Dhruv. Arvind sits at the top of this ranking.
Final Answer:
Arvind holds the highest starting salary of Rs 70,000.
\[ \boxed{\text{Arvind}} \]