Copy and insert rows n number of times + operations on data

Hi
I am a total beginner and i am trying to write a macro to do some operations on a dataset, but I cannot get through it. can someone help me? thanx!

The start matrix
A B C
row1 abc def 3
row2 ghi lmn 2

the matrix must be copied on a different sheet than i need to replicate each row as many times as indicated in column c + fill in an extra cell (column D) that concatenates the content of cell B and C

in practice, the result to be obtained

A B C D
row1 abc def 3 def1
row2 abc def 3 def2
row3 abc def 3 def3
row4 ghi lmn 2 lmn1
row5 ghi lmn 2 lmn2

i will really appreciate any help! thanx a million!