I am trying to insert a formula box with an If condition but I am continiosuly getting error called "Missing Quotes"

My if condition contains strings

If('${SalesOrders.Deal Type}'=='Influenced',${SalesOrders.Grand Total}/2,${SalesOrders.Grand Total})

I have a field called deal type,  what I am trying to write is if the deal type field contains the string "Influenced" then the return value should be 50% of the Grand Total.

Somebody please help me with an accurate syntax

Thanks!

Suraj