The language of the section is :
"In order to widen the tax base vis-à-vis profit linked deductions, it is proposed to amend provisions regarding AMT contained in Chapter XII-BA in the Income-tax Act to provide that a person other than a company, who has claimed deduction under any section (other than section 80P) included in Chapter VI-A under the heading “C – Deductions in respect of certain incomes” or under section 10AA, shall be liable to pay AMT. "
and
"
It is further provided that the provisions of AMT under Chapter XII-BA shall not apply to an individual or a Hindu undivided family or an association of persons or a body of individuals (whether incorporated or not) or an artificial juridical person referred to in section 2(31)(vii) if the adjusted total income of such person does not exceed twenty lakh rupees."
Good observation...Mr. Shyamal Mistry..
It means AMT is applicable to firms but the limit of Rs. 20 Lacs is not applicable to firms..