Clarification regarding VAT and Service Tax

Sir,

I'm interested in buying a flat under construction from a reputed builder but I think that the VAT and Service Tax are overcharged. VAT is calculated as follows:-

Basic cost (Super built up area x rate/sq ft) + car parking + club house chgs + generator chgs + gas bank chgs + infrastructure devpt chgs = X - Y (land cost of undivided area) = Z

VAT = Z x 9.8%

Service Tax = Z x 4.12%

Are the above  items all inclusive in the calculation of VAT and Service tax?

I've heard that VAT is 4% under composite scheme why is it 9.8%

and I've heard that Service tax is calculated as 10.3% of 33% of value = 3.4% ( not 4.12% as calculated)

KIndly clarify

Lakshmi