I am doing a homework problem for my management class that states "Insert a lookup function in cell H5 to display the amount of down payment for the...

I am doing a homework problem for my management class that states "Insert a lookup function in cell H5 to display the amount of down payment for the first client based on the membership type." This is for a problem in excel. So I came up with this formula, 

=VLOOKUP(B5,MEMBERSHIP+B4,3,FALSE) but every time I put it in, it says "#NAME?" why is it saying this? why isn't my formula correct?