A 45-year old man is O, Rh negative with anti-K.  Given the…

A 45-year old man is O, Rh negative with anti-K.  Given the following population statistics, how many O negative donor units should be typed in order to find 3 that are K negative?            POPULATIONPhenotype             FrequencyK+k-                        0.2%K+k+                       8.8%K-k+                         91%K-k-                         rare