Coordinate Transformations

In the case of a Least Squares transformation between a source and a target coordinate frame, using
i. 2D four-parameter (Conformal),
ii. six-parameter (Affine) and
iii. eight-parameter (Perspective) transformations,
answer the following three questions:
1. What is the minimum number of common points required to determine the transformation parameters in the case of the three transformations?
2. What affect does the transformation type have on the goodness-of-fit of both
coordinate frames?
3. What distortions in a source frame may be removed by each of the three transformations?