The cross section AB is given below. The topography can be assumed to be gently undulating at an elevation of 500 to 650 m. Thus at the scale of the map (N.B. the vertical and horizontal scales are the same) topography can be assumed to be approximately flat. Note that the S101 rock unit is a subhorizontal hillcapping unit. The alluvium consists of thin units (< 20 m) of gravel, sand, and mud in the lowest parts of the main valleys in the map area (not shown on the cross section). (a) What is the type of contact between the S101 rock unit and the underlying rock units (A43, C1, A126)? (b) List in point form the geological history of the map area. (c) Comment on the suitability of serpentinite for engineering purposes