In these writ petitions, the petitioners have prayed for issue of a writ of mandamus forbearing the respondents from recovering or enforcing the demand towards alleged difference by way of final cost and tentative cost of M.I.G. flats with respect to the members of the petitioner’s associations whose names are set out in the schedules to the petitions. The members of the associations were allotted middle income group flats in 1979-80. With respect to the petitioner association in W.P.No.7061 of 1986 the allotment letter was issued on 23. 1980. Tentative cost was fixed at Rs.42,200 for ground floor and first floor and Rs.40,100 for the second floor. Clause 9 of t he letter which is the crucial clause reads thus:

“Final cost of the flat will be intimated within a period of 3 years. The difference of cost if any is to be paid in one lump sum or in monthly instalment from the beginning.”

It is only in 1986 the respondents demanded additional payment from the petitioners on the footing that final cost is fixed at a higher rate. Difference varies from Rs.6,900 to Rs.14,300 per flat. Aggrieved by the same, the petitioners have preferred these writ petitions.

2. In a similar ca