Linear interpolation of rates

[Finkid]

Hello guys,
I am confused about how to do interpolation when rates are presented in the following form?
0-7 days
9.68%
8-15 days
9.71%
16-30 days
9.70%
31-60 days
9.58%
The linear interpolation formula I am using is
Interpolated rate = short term rate + ((long term rate - short term rate)/Days long term - days short term)) * (days of the desired rate - days short term)
I am confused as to how to calculate “days long term” and “days short term”.
Also, please tell what would be the 34 day interpolated rate?
Thanks

 

[S2000magician]

I’d pick the midpoint of each range as the number of days.
So, 9.68% applies to 3.5 days, 9.71% applies to 11.5 days, and so on.

 

[Finkid]

will be it okay if use 7 days and 30 days for interpolation of 14 day rate?