With
K1:L4 containing this list
Power Tools                   0.04348
Home & Garden                 0.0957
Vehicle Parts & Accessories   0.06957
Business Office & Industrial  0.0957
and
D2: a data validation cell that uses the list in K1:K4

This regular formula uses the D2 selection to specify the Col_L value to use in the calculation
G2: =J2*INDEX($L$1:$L$4,MATCH(D2,$K$1:$K$4,0))
Note: The SUM function is unnecessary because you aren't adding any values together

Is that something you can work with?