In the diagram, \triangle{PQR} has PQ=QR=RP=30. Points S and T are on PQ and PR, respectively, so that ST is parallel to QR. Points V and U are on QR so that TU is parallel to PQ and SV is parallel to PR. If VS+ST+TU=35, the length of VU is
Answer Choices
A. 21
B. 15
C. 18
D. 20
E. 25