(Solved): (10\%) Problem 9: Some physies students are studying periodic motion using an oscillating mass on a ...

(10\%) Problem 9: Some physies students are studying periodic motion using an oscillating mass on a spring. After recording duta, they made the position wersus time graph shown. The function that represents the data on the graph may be written as $$x=A\cos (?t+?)\text{ with }??[0,2?)$$ If the spring constant is $$6.79\mathrm{N}/\mathrm{m}$$, then what is the mass, in kilograms?