How does the $80/20$ rule apply to coding and software development?

a$.$

It suggests that $80\%$ of coding time should be spent on testing and debugging.

b$.$

It states that $20\%$ of code should be written by senior developers, while $80\%$ can be written by junior developers.

c$.$

It emphasizes that $80\%$ of the code should focus on core functionality, while $20\%$ can handle edge cases.

d$.$

It implies that $80\%$ of software development can be completed in $20\%$ of the estimated time.