如果part sale, part gift, the transfee's basis = greater of

1. amt paid by the trsfee or 2. trsfor's adjusted basis, for example, A sold to son: $60,000, FMV: $90,000, Adj basis: $45,000
Gain = $60K-45K = $15K, son's basis: $60K。 同样，如果 gift tax paid allows donee to increase the donee's basis.