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

### Instruction:
A hurricane is approaching the southern coast of Texas, and a rancher is planning to move 400 head of cattle 60 miles to higher ground to protect them from possible inland flooding that might occur.  His animal transport truck holds 20 head of cattle.  Traveling at 60 miles per hour, what is the total driving time, in hours, it will take to transport all of his cattle to higher ground?

### Response:
Given the limited capacity of the transport vehicle (20 head of cattle) and the total number of cattle to be moved (400 head), the number of trips required is 400/20=<<400/20=20>>20 trips.
Traveling to the site at 60 mph for 60 miles it will take 60/60=<<60/60=1>>1 hour to travel one-way.
Since each trip requires driving to and returning from the relocation site, each complete round trip will take 2*1=<<2*1=2>>2 hours.
Since there are 20 complete trips required, the total driving time will be 2*20=<<2*20=40>>40 hours of driving time.
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