<prompt> A 56-year old woman has a mean systemic blood pressure of 100 mm Hg and a resting cardiac output of 4 Lmin. What is the total peripheral resistance of this woman?0.025 mLminmm Hg0.025 mm HgmLmin40 mLminmm Hg40 mm HgminmL  <response>: Total peripheral resistance TPR is equal to the pressure gradient across the circulation mean aerial pressure - right atrial pressure divided by the cardiac output. Right atrial pressure is assumed to equal 0 mm Hg. Thus, TPR 1004000 0.025 mm HgmLmin. The ABC rule is useful in remembering the relation between pressure P, flow Q, and resistance R because PQR P,Q and R in alphabetical order. Tip: Note that choices A, C, D can be eliminated quickly because in each case the units are incorrect. 