In rectangle ABCD, AB=6 and BC=3. Point E between B and C, and point F between E and C are such that BE=EF=FC. Segments AE and AF intersect BD at P and Q, respectively. The ratio BP:PQ:QD can be written as r:s:t, where the greatest common factor of r,s and t is 1. What is r+s+t?<spanclass=′latex−bold′>(A)</span>7<spanclass=′latex−bold′>(B)</span>9<spanclass=′latex−bold′>(C)</span>12<spanclass=′latex−bold′>(D)</span>15<spanclass=′latex−bold′>(E)</span>20