Below is an instruction that describes a task. Write a response that appropriately completes the request in Swahili. Please answer in Swahili.

### Instruction:
Three planes are going to the same place but each has a different number of passengers. The first plane has 50, the second had 60, and the third has 40. An empty plane can go 600 MPH, but each passenger makes it go 2 MPH slower. What is their average speed?

### Response:
 Ndege ya kwanza inakwenda kwa kasi ya maili 100 chini ya ndege tupu kwa sababu 50 x 2 = <<50*2=100>>100
Ndege ya kwanza inakwenda kwa kasi ya maili 500 kwa sababu 600 - 100 = <<600-100=500>>500
Ndege ya pili inakwenda kwa kasi ya maili 120 chini kwa sababu 60 x 2 = <<60*2=120>>120
Ndege ya pili inakwenda kwa kasi ya maili 480 kwa sababu 600 - 120 = <<600-120=480>>480
Ndege ya tatu inakwenda kwa kasi ya maili 80 chini kwa sababu 40 x 2 = <<40*2=80>>80
Ndege ya tatu inakwenda kwa kasi ya maili 520 kwa sababu 600 - 80 = 520
Kasi jumla ni maili 1500 kwa sababu 500 + 480 + 520 = <<500+480+520=1500>>1500
Kasi yao ya wastani ni maili 500 kwa sababu 1500 / 3 = <<1500/3=500>>500