We prove a formula for the push-forward class of Bott-Samelson resolutions in the algebraic
cobordism ring of the ag bundle. We specialise our formula to connective K-theory providing
a geometric interpretation to the double -polynomials of Fomin and Kirillov by computing the
fundamental classes of Schubert varieties. As a corollary we obtain a Thom-Porteous formula
generalising those of the Chow ring and of the Grothendieck ring of vector bundles.