Team B needs 45 days alone. Daily workload: 1/45.
Group C needs 60 days. Daily workload: 1/60.
In order to shorten the construction period as much as possible, Party A, Party B and Party C need to make joint efforts, and the proportion of their workload to the total workload is as follows:
A: (1/30)/(1/30+1/45+1/60) = 6/13.
b:( 1/45)/( 1/30+ 1/45+ 1/60)= 4/ 13。
( 1/60)/( 1/30+ 1/45+ 1/60) = 3/ 13.
So the task assignment is:
A: 1300*(6/ 13)=600 meters.
B:1300 * (4/13) = 400 meters.
C: 1300 * (3/ 13) = 300m。