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: Ingratitude stings strongest where relationship is closest.
P: Expectation turns innocent relationship into commerce.
Q: Human relationship is adulterated with sly commerce.
R: In commerce, of course, give and take is understood.
S: Most relationships are founded on mutual expectations.
S6: From any warm and healthy human relationship expectation of returns has to be weeded out.
The Proper sequence should be: