Every contract entered into by either of the two companies in relation to any of 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 a period of one hundred and eighty days from such day, cease to have effect unless such contract is, before the expiry of that period, ratified, in writing, by the Central Government or the existing, or new, Government company and in ratifying such contract, the Central Government or the existing, or new, Government company may make such alteration or modification therein as it may think fit:
     Provided that the Central Government or the existing, or new, Government company shall not omit to ratify a 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 such Government company; and
         (b) except after giving 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.