On determinant preserver problems

Let Mn and Tn be the vector spaces of n×n matrices and upper triangular matrices over a field (with some cardinality and characteristic restrictions) respectively. We characterise transformations φ on these two spaces separately which satisfy one of the following conditions: 1. det(A+λB)=det(φ(A)+λφ(B)) for all A, B and λ.2. φ is surjective and det(A+λB)=det(φ(A)+λφ(B)) for all A, B and two specific λ.3. φ is additive and preserves determinant.