Question 1198025
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Notebooks may be bought in bulk. If you can avail the first 10 notebooks at Php 15 each, 
and every piece of notebook thereafter costs Php 20, make a linear equation for this. 
Sketch the graph of the linear equation.
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For the further generations of students, who will read this post:


<pre>
    There is no any equation relevant to this problem - there is only function,
    relevant to it.

    The relevant function is not linear: it is piece-wise linear function,
    so you better ignore this post since it is worded incorrectly.
</pre>