nested IF calculation

I am trying to make a formula in column D that tests a column of data points (A) against a range (B) and then uses a multiplier (C) to get a result while adding to it ranges/results below the value of that data point. For example attached in file Book2.xls, the data point 15.34 is between 11.674 and 17.96. Therefore the answer I want is (8.98*.122) + (11.674-8.98)*.139 + (15.34-11.674)*.302 = 2.577. For the data point 6.32, then it is simply 6.32*.122= .771. I think I need to use nested IF's but not sure how?