The Putnam Estimation Model is a dynamic multivariable model that assumes a specific distribution of effort over the life of a software development project. The model has been derived from manpower distributions encountered on large projects total effort of 30 man- years or more). However, extrapolation to smaller software projects is possible, In Putnam model there is only one choice with the manager to use for cost estimation. Thus, the estimation is very restricted. Now we want that the manager should have some choice while estimating the value of K & td (and thus cost estimations). So, in this paper, we want is to find a zone solution to the equations, so that manager can choose the value of & as per his requirement within that solution zone. By doing so we can make the estimation more general.