construction contract (MCQ mock exam question)

Q: on 1 jan, 2013 Agnes entered into a construction contract that is expected to last 36 months. The agreed price for the construction work was 20mil. As at 30 sept,2013 the costs incurred on the contract were $4mil and the estimated costs to complete the contract were $12mil. In addition to the above costs on 1 July, 2013 Agnes acquired for exclusive use on the contract an item of plant for $1mil. This plant has an estimated useful life of 2 years and will be scrapped at the end of that time. On 20 Sep,2013 Adriadne received a payment from the customer of $7mil which amount was equal to the progress billings to date. Adriadne calculates the stage of completion on construction contracts on the basis of progress billings as a proportion of the contract price What amount would be reported in Ariadne's statement of financial position sa at 30 Sep 2013 for the amount due to/from the customer for the above contract? A: since % of completion is according to progress billing over contract price thus on 20 Sep 2013, the % completion = 7/20*100%= 35% w1 Rev Recognised $20mil * 35% = $7mil cost incurred on contract general = ($4mil+$12mil)*0.35=$ 5.6mil cost recognised specific = $1mil (3/24)=$0.125mil total cost recognised=5.6+0.125= $5.725mil profit reg=7-5.725=$1.275mil w2 cost incurred to date =$4mil profit recog= $1.275mil progress billing to date=$7mil amt due to/from customer = 4+1.275-7= ($1.725mil) thus $1,725,000 liability but there's no option of this in answer, instead $ 1,600,000 liability is the correct answer, may i know why?