In all you have 54 buttons because if you add 10 plus 10 that equals 20 plus 34 and that gets 54 buttons in all
Answer:

Step-by-step explanation:
There is no graph posted, but y-intercepts are <em>x</em>'s are set equal to zero.
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The slope f'(x) = [f(4) - f(2)]/(4-2)≥3,
so [f(4) - 13]/2 ≥3
f(4) -13 ≥ 6
f(4)≥19, so it can be as small as 19.