Find all isolated singularities of the following functions and classify them as removable singularities, poles, and essential singularities. If it is a pole, also specify its order. (a) f 1
​
(z)= (z−1)(z+e)
z 3
−1
​
[4] (b) f 2
​
(z)= (z 2
+4)
1
​
⋅e 1/z
[4] (c) f 3
​
(z)= z 5
cos(z 2
)−1
​
. (Hint : Consider the Taylor series T f 3
​
​
(z) ). [4]