Semi-Direct Product: Homomorphisms, Generators, Relations & Isomorphism Types

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thnx for helping on the previous post.

heres the next one, as usual any hints on how to approach the question would be greatly appreciated. i will attempt the questions with the hints :)

(1)
describe explicitly all homomorphisms

\varphi : C_4 \rightarrow Aut(C_5)

(2)
For each such homomorphism \varphi describe the semidirect product C_5 \rtimes_{\varphi} C_4 in terms of generators and relations.

(3) How many distinct isomorphism types of groups of the form C_5 \rtimes_{\varphi} C_4 are there?
 
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It will help to know what Aut(C_5) is. Hint: It's cyclic.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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