I am struggling to return a value in a formulae,

Heres my example 155 needs to return 2.50% and 555 would be 7.50%

1 50 0.00%
51 250 2.50%
251 500 5.00%
501 1,000 7.50%
1,001 2,500 10.00%
2,501 5,000 12.50%
5,001 10,000 15.00%

I have tried multiple =if( but am failing badly

Thx