Explanation:

- The area of the square park is $18\text{m}\times 18\text{m}=324{\text{m}}^2$.

- The park with the pavement has a side of $18\text{m}+5\text{m}+5\text{m}=28\text{m}$.

- The area of this larger square is $28\text{m}\times 28\text{m}=784{\text{m}}^2$.

- The area of the pavement is $784{\text{m}}^2-324{\text{m}}^2=460{\text{m}}^2$.

- The cost of cementing the pavement is $460{\text{m}}^2\times 15{\text{Rs/m}}^2=6900\text{Rs}$.

Options provided do not match the calculated cost:

- Option 1: Rs. 5000

- Option 2: Rs. 4750

- Option 3: Rs. 4360

- Option 4: Rs. 4380

- Option 5: None of these

With this, the correct answer is:

- Option 5: None of these