Determine value based on whether a customer name is in a list

I have two columns - one with customer name (A1), another with a number (B1)

What I want is, IF A1 equals a specific Customer name taken from a list, then return 14 in B1 (Being the number of days they have to pay), otherwise it just returns a 7.

Currently my formula is =IF(A1="Customer1","14","7") Which is great, but only allows for one customer. I need it to do the formula, but if A1 contains a name from a list of names then returns 14 otherwise it is 7. I can put the list on a different tab.

Please help!