I need new guy friends lol and help with GST

Triangle U S T is shown. Angle U S T is 100 degrees. The length of U S is 9, the length of S T is 10, and the length of U T is s.
Which equation correctly uses the law of cosines to solve for the length s?

92 = s2 + 102 – 2(s)(10)cos(100°)
9 = s + 10 – 2(s)(10)cos(100°)
102 = s2 + 100 – 2(s)(10)cos(100°)
s2 = 92 + 102 – 2(9)(10)cos(100°)

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