Protect them from what? The beast the Indian navy will be in the future? Good luck.
You should spend $10 billion.
You Indians are really funny.
Two reasons why BD military is so weak:
1. Very tiny economy in the past which is fixed now.
2. Very low percentage of GDP devoted to military in the past 4 decades - around half that of India on average.
All that BD needs to do is raise military spending to 2.5-3% of GDP and see how powerful a defensive force BD becomes in 15 years time.
Yes India can take this on at the cost of losing pretty much their whole Navy in the eastern sector.