Income Tax on Pension commutation

My Father is just retired. He got the gratuity. He is also eligible to get the pension. He has commuted his 40% of the monthly pension value. I want to know the income tax liability on the commuted pension amount.

He total monthly pension is calculated as 10000/- pm & he has commuted 4000/- pm & got around 450,000/- as the commuted value. I want to know how much amount out of this 450000/- will be taxable? (Pls note that he also got the gratuity).