A BaSO4 slurry is ingested before the gastrointestinal tract is x-rayed because it is opaque to x-rays and defines the contours of the tract. Ba2+ ion is toxic, but the compound is nearly insoluble. If ΔG° at 37°C (body temperature) is 58.5 kJ/mol for the process what is [Ba2+] in the intestinal tract in units of micromolar? (1 micromolar = 1x10-6 molar)? (Assume that the only source of SO42− is the ingested slurry.)