Cost of living in Jakarta in 20 million rupiah (IDR) per month?

I am an Indian, would be soon moving to Jakarta with my wife and one 5 year old kid in July 2011. My company is offering me 20 million rupiah (IDR) per month. Here in India my and my spouse collective salary is good and we save Rs. 1,30,000/- per month. In Jakarta in 20 million IDR how much would we be able to save? Accomodation, car and kid schooling is taken care by my employer. Also in Jakarta my wife will not be working. Please tell me is this salary of 20 million IDR ok? How much will the tax be deducted? How much would be other expenses like - grocery, maid, dresses, electricity etc. Please guide.