WX acquired 20% of the equity share capital of MN for $135 million in 20X5. WX acquired a further 40% of the equity share capital of MN for $400 million on 1 October 20X8 when the fair value of the net assets of MN were $800 million.

The fair value of the initial 20% investment in MN was $175 million at 1 October 20X8. There has been no impairment of the investment in MN. WX uses the proportion of net assets method to value non-controlling interest at acquisition.

Calculate the goodwill arising on the acquisition of MN.

Give your answer to the nearest $ million.

 $ ?  million