Об­ра­зуй­те от слова DIFFER од­но­ко­рен­ное слово так, чтобы оно грам­ма­ти­че­ски и лек­си­че­ски со­от­вет­ство­ва­ло со­дер­жа­нию тек­ста.

Probably my biggest contribution is to advise them of the most efficient way to invest in their businesses. Very often, a small change can make a big ______ in business. When they take my advice and I see a new company or business begin to succeed  — it is really satisfying. I feel as if I was part of the success story and a member of their team.