Estimated cost of completion

For construction contract, what amount should be included in the “Estimated cost to completion” to determine the estimated profit?

Let say the contract started on 1 April 2010, but they provided you with a figure for estimated cost at start of contract which is, 15 million, and the estimated cost at 31 March 2012 to completion is 3.5 m?

Find out the estimated profit with the above information.