It takes x, y and z days to form a, b and c teams respectively.

Yes:1/x+1/y =1/6.

1/y+ 1/z = 1/ 10

1/x+ 1/z=2/3/5

Then x = 10, y = 15 and z = 30.

Set up three teams, A, B and C respectively, with a daily salary of X, Y and Z yuan.

There are:

(x+y)*6=8700

(y+z)* 10=9500

(x+z)*5=5500

Then x = 800, y = 650 and z = 300.

If it is completed within 15 days, both parties can be competent.

What wages do they need respectively

800* 10=8000

650* 15=9750

So it is the most economical to finish it by team A alone.