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Assuming that TWQ is a diameter, angle(PWT)  =  180^o - 128^o  =  52^o.

Assuming that PWR is a diameter, angle(TWS)  =  180^o - 31^o - 52^o  =  97^o.

Thus, arc(TS) is 97/360^th of the circumference of the circle:  (97/360)·2·pi·(4.5)  =