<prompt>  The positive inotropic effect of digitalis is due to inhibition of NaK ATPase pump in cardiac muscle cell membrane leading to:Decreased activity of NaCa exchanger causing decreased influx of sodium and decreased efflux of Ca in the sarcolemmaDecreased efflux of Na leading to less negative resting membrane potential and opening of voltage gated Ca channels on the T tubulesIncreased intracellular Na causing increased efflux of Na and increased influx of Ca through NaCa exchanger in the sarcolemmaIncreased intracellular Na decreasing the activity of Ca pump in the sarcoplasmic reticulum 