Assuming that Winston Churchill looks at the losses to shipping from u-boats in early 1942 and decides that one way to help the logistical situation is to build a railway connecting the Indian and Persian networks (allowing Indian troops and supplies to be moved back and forth to the Middle-East without the need for ships moving across the Arabian Sea) how long would it take to actually build such a line and to get it running if the go-ahead is given in May 1942?