In each question, the first and the last sentences of the passage are numbered S1 and S6 respectively. The rest of the passage is split into four parts. These four sentences are jumbled. Read the sentences and identify their correct and logical order.

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S1: We don't know whether the machines are the masters or we are.
P: They must be given or rather 'fed' with coal and given petrol to drink from time to time.
Q: Already man spends most of his time looking after and waiting upon them.
R: Yet he has grown so dependent on them that they have almost become the masters now.
S: It is very true that they were made for the sole purpose of being man's servants.
S6: And if they don't get their meals when they expect them, they will just refuse to work.
The Proper sequence should be: