if statement with condition

hello all....

i'm currently experiencing some problems with my if statements

basically i have 4 scenarios in there...im just not sure if my logic is correct or if im missing something....the formula is as follows:

=IF(O12<0,"",IF(O12>0.1<4.3333,'Lookup Up'!$T$2,IF(O12>4.3334<8.3333,'Lookup Up'!$T$3,IF(O12>8.3334<12.9999,'Lookup Up'!$T$4,BB$9))))

im asking the formula for the following....
O is # of weeks a person has worked in total
...so basically
-scenario #1 is saying....if they have worked b/w 0.1-4.3333 weeks, then lookup value in sheet "lookup" (which is $75)

-scenario #2 is saying....if they worked b/w 4.3334-8.3333 weeks, then lookup value in sheet "lookup" (which is $100)

-scenario #3 is saying...if they worked b/w 8.3334-12.9999 weeks, then lookup value in sheet "lookup" (which is $150)

- if none of those scenarios are true (if person has worked greater than 13 weeks, then make the value = $200 (BB$9 - reference)


...now when i do this, it gives me $200, its not for some reason its not applying the logic in scenario #1, 2 or 3.........hope you guys follow and can help, pls and thxs