Every contract entered into by the Company in relation to its undertakings, which has vested in the Central Government under section 3, for any service, sale or supply and in force immediately before the appointed day, shall, on and from the expiry of one hundred and eighty days from the appointed day, cease to have effect unless such contract is, before the expiry of that period, ratified, in writing, by the Central Government or the Cement Corporation, where such undertakings have been vested in that Corporation under this Act, and in ratifying such contract, the Central Government or the Cement Corporation may make such alteration or modification therein as it may think fit:
     Provided that the Central Government or the Cement Corporation shall not omit to ratify contract and shall not make any alteration or modification in a contract--
         (a) unless it is satisfied that such contract is unduly onerous or has been entered into in bad faith or is detrimental to the interests of the Central Government or the Cement Corporation, and
         (b) except after giving to the parties to the contract a reasonable opportunity of being heard and except after recording in writing its reasons for refusal to ratify the contract or for making any alteration or modification therein.