I need to construct a formula with the following parameters:

If L7 is
<=15 return 1.0
between 15.1 and 15.4 return 2.5
between 15.5 and 15.9 return 4.0
between 16.0 and 16.9 return 5.5
between 17.0 and 17.9 return 6.5
between 18.0 and 18.9 return 7.0

and so on.

Any help appreciated.