If any assessee fails, without, reasonable cause to make
payment of any amount of tax within the time specified in
the notice of demand, the assessing authority may, after
giving him a reasonable opportunity of making his
representation, impose upon him a penalty which shall not
be less than twenty-five per cent but not exceeding fifty
percent of the amount of tax due. This penalty shall be in
addition to the interest payable under sub-section (1) or
sub-section (2) of section 11.