Calculation of MVAT 2012 for Purchase of Under construction flat

I request your help in an old case pertaining to demand of VAT by builder for purchase of under construction flat in the year January 2010.

The builder has demanded 5% VAT of the agreement value. However according to my calculation the VAT could be much lower under Standard Deduction formula.

I'm able to calculate the taxable sales value under Standard Deduction by first deducting the land value and then deducting 30% from remaining contract value.

Please help me determine how much tax setoff / input tax credit can be deducted after calculating 5% VAT on this contract value.

Let us assume that builder has not kept any books of accounts, so what could be the input tax credit / setoff applicable u/r 52 and 55.