Simple...
multiplying your binomial you get a GREAT number..but....I will only list a few..and I will give you the fourth term you seek...
[tex] e^{10} + 20e^{9} f+ 180e^{8} f^{2} +960e^{7} f^{3} +3360 e^{6} f^{4} [/tex]....(etc)
As you can see...the forth term is [tex]960 e^{7} f^{3} [/tex]
Thud, your answer.
