150-x≥2x，x≤50。

If the employed workers need to pay a monthly salary of Y yuan, then

y=600x+ 1000( 150-x)

∴y=-400x+ 150000(0≤x≤50)

∴y decreases with the increase of x,

When x=50, y is the smallest.

y =-400×50+ 150000 = 130000

150-x= 100

Fifty people. B: 100 people. Total salary:130,000 yuan.