def calc_COsld(param, dbin, zprofsmooth, vfprofsmooth, sldprofsmooth,bulk_sld):
	z, A= param
	SLDfit=A*(vfprot*sldprot)+A*(1-vfprot)*bulk_sld+(1-A)*bulk_sld
	SLDfitArea = numpy.sum(SLDfit*dbin)
	COsld = (1/SLDfitArea)*(numpy.sum(SLDfit*zprofsmooth))+z
	return COsld