Problem from dipole moment which involves perimeter of elipse

An ellipse has a uniform linear positive charge density in upper half (total upper half part charge $+Q$ ) and a uniform linear negative charge density in lower half (total lower half part charge $-Q$ ) as shown in figure. Here, semi-minor axis $b<a$ semi-major axis. Select the correct statement about the magnitude of electric dipole moment $p$ of the ellipse.

options are

To do it by calculus we need charge per unit length but i recently watched a youtube video stating that there is definite formulae of perimeter of elipse and there are only approximations.
Here is the video link
https://youtu.be/5nW3nJhBHL0