What does 'plum job' and 'to take sth all in mean'?

[Me]

hi Alan and Torsten!!

Test No. incompl/inter-4 "Easy Questions", question 4

He is very lucky to have got himself a ......... job.

(a) pear
(b) banana
(c) lemon
(d) plum

Test No. incompl/inter-4 "Easy Questions", answer 4

He is very lucky to have got himself a plum job.

Correct answer: (d) plum

What does "plum job" and "to take sth all in mean"? Thanks for the answer in advance!!

[Alan]

This means the best job available - one that everybody would like.

Alan
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English as a Second Language
You can read my ESL story Only Three Letters

[Miklos]

Dear Alan,

Could you explain the origin of this expression, please? Is it related to fruit picking somehow?

Sincerely,
Miklos