how to reduce the project duration by four weeks

Question

plz tell me how to reduce the project duration by four weeks(5 option)?
These are my task list

1. Strategic Study - 2 weeks
2. Business Study - 3 weeks
3. Feasibility Study - 2 weeks
4. Requirement Analysis - 4 weeks
5. Requirement Specification - 5 weeks
6. Design - 2 weeks
7. Testing - 3 weeks
8. Implementation - 3 weeks
9. Maintenance - 2 weeks
10. Sign off - 2 weeks

Thank U