How to use interpolation to estimate the median, Q1 and Q3??

can someone tell me how do you use interpolation to estiamate the Q1,Q2, and Q3?

Thanks in advance.

BTW here is an example to use-------------------->>>>>

The values of daily sales, to the nearest £, taken at a newsagents last year are summarised in the table below.

Sales Number of days
1 – 200 166
201 – 400 100
401 – 700 59
701 – 1000 30
1001 – 1500 5

(b) Use interpolation to estimate the median and inter-quartile range of daily sales.