The absorptivity often used in rapid determinations of protein concentration is the E^1%, based on aromatic amino acid absorbance at 280nm in a 1 cm pathlength. The E^1% employed for a mixture of proteins is 15. (The E^1% is the absorbance of a 1% (w/v) solution.) A solution of proteins diluted 1 in 30 gives an A280 of 0.25. What is the concentration of protein in the undiluted sample?