Excel 2008 : RESOLVED Configuring Nested IF Logic

I am trying to generate an IF statement that will take the data in cell D7 and if it is more than 4 the result is 15, if it is between 2 and 4 years, the result is 10, if it is between 1 and 2 years, the result is 5, if it is less than 1, the result is 0.

What I have is =IF(AND(B7="FT",D7>=4),15,IF(OR(B7="FT",D7>=2<=4),10,IF(OR(B7="FT",D7>=1<=2),5,
IF(OR(B7="FT",D7=0),0)))

The result is always 10, even if the cell is 4 or greater.

What have I got that is wrong and can you help?

Excel 2010 on the Windows Partition
Excel 2011 on the Mac Partition.