An observer want to observe a line of strength 250 Jy at 40 
m, reaching a
S/N of 30 and covering 200 km/s. From figure 6.5 we see that we
reach a S/N of 10 on a 700 Jy source in 1200 seconds while scanning 50 km/s.
Therefore to reach 250 Jy with 150 km/s will take
seconds. This is over 10 hours so
the observation cannot be planned. However, to scan 80 km/s to a S/N of 15
will take 34000 seconds. PGA reports this observation is feasible and will
require 29000 seconds OTT.