Question 1198025
first 10 notebooks at Php 15 each, and every piece of notebook thereafter costs Php 20
 C = 20(x-10) + 150
 C = 20x -200 + 150
 C = 20x - 50
{{{drawing(300,300,    -20,20,-100,100,   
 grid(1),
circle(0, -50,0.6),

graph( 300, 300, -20,20,-100,100,0, 20x-50))}}}