A radiograph of the upper ribs demonstrate the diaphragm is…

A rаdiоgrаph оf the upper ribs demоnstrаte the diaphragm is superimposed over the seventh to eighth ribs, which is the area of interest.  The following exposure factors below were used.  Which of these factors below can be modified to increase the visibility of the area of interest? 75kV 400mA 1/40sec suspended respiration on expiration erect position 40" SID