A stationery shop orders a batch of pens from a factory.
The factory could make the batch of pens in
20 days using 12 machines.
Due to a fault, only 8 machines were used for the
first 9 days.
All 12 machines were used from day 10 onwards.

Work out the total number of days taken to make
the batch of pens.

Idon’t exactly understand but i think dbc=rst

For range i think it’s area

The question is kind of confusing. if it's asking how many variations of answers can you give. then do 4^5 for your answer.this would be something like the first question could be a and the 2nd c or first b next c etc. if you can, ask the teacher for a better confirmation of what it's asking. if i'm assuming correctly what it's asking, it's 625 different variations.