Use Case -- Study

Dears,

I need some support and hints to solve this use case:

Thanks

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You are in the middle of a small Software development project which is supposed to last for few months and staffed with one development team. The scope was initially estimated at 84 Story Points (SP). The team works in iterations (Sprints), five of which have been completed.

Sprint   Velocity(SP)

1                  2

2                 10

3                 18

4                 18