Ethical risks

Hello sir. I would like to ask if a company is listed, is it allowed to an audit firm to supply other services when it has also the audit engagement?

And also in BPP there is an example which does not provide which threat is that (self interest???).
Salt & Pepper guarantees that its audits will not last
longer than two weeks.
The amount of time required to complete an audit
depends upon the nature of each audit client’s
business and the level of associated risk. To restrict
the duration of all audits to two weeks, regardless of
the level of complexity and risks of the business, will
result in sufficient and appropriate audit evidence
not being obtained. Salt & Pepper would be at risk of
giving incorrect audit opinions, leading to possible
litigation. The firm would contravene the ACCA Code
of Ethics.

Thank you very much.