Reference Table
 

This is the table I have:

A B

33 5.5462
62 5.5556
90 5.5524
182 5.5220

column A represent a number of days and B interest rate values.

I'm looking for a formula that will return the interest rate of any
given day that is in between 33 and 182.
So if the number of days is 33, it will return 5.5462.
But if it is 40, it will find the interest rate using interpolation
from the closet values (i.e., 33, 62, 5.5462 and 5.5556). I know how to
make the interpolation work I just need the formula for the reference.

Thanks.