According to Hooke's law, the force required to compress or stretch a spring from an equilibrium position is given by F(x)=kx, for some constant k. The value of k (measured in force units per unit length) depends on the physical characteristics of the spring. The constant k is called the spring constant and is always positive. In this problem we assume that the force applied doesn't distort the metal in the spring.
Part 1.

A 2 m spring requires 10 J to stretch to 2.5 m.
Find the force function, F(x), for the spring described.

F(x)=
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Note: enter your answer using values correct to three decimal places.

Part 2.

How much work is required to stretch the spring to 2.8 m?
W=
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Note: enter your answer using values correct to three decimal places.