The conditions in a TEMPO apply for less than half the
time. If the question asks "What is most likely ?"
then you ignore the TEMPO because most of the time you will have the permanent
conditions. If the question asks "What is the lowest/worst forecast ?" or "What is the lowest/worst
possible/probable ?" then you would include the TEMPO conditions because
it could happen.
BECMG 1314 9000 means that between 1300hrs and 1400hrs
the visibility will change to 9,000m. The change will not start
until after 1300hrs but will be complete by 1400hrs.