Help! Need to calculate bonuses based on years and salary.....

I am stuck and need some help.

I have to calculate bonuses for employees using IF statements based on their salary, age (no bonus until 50) and years of employment. I have the table set up as follows:
Employee Age Length of Service Salary

<5 = 0 bonus
5-10 =20%
11-15=30%
16-20=40%
21-25=50%
26 or more =100% of yearly salary

I am very stuck and really could use some advise.

Thank you so much in advance. I am starting to see stars with my frustration.....

Try

=LOOKUP(A1,{0,5,11,16,21,26},{0,20%,30%,40%,50%,100%})

Also your data is wrong 20 years service, is that 40% or 50% cos 20 is listed against BOTH percentages (I've assumed 20 is 40%)