For two sets $A=\{(x,y) \mid y=x^2-ax+48\}, B=\{(x,y) \mid y=0\},$ what is the minimum value of a positive integer $a$ that satisfies $n(A \cap B)=2?$

Note: $n(X)$ is the number of the elements of the set $X.$

14
12
13
11

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Its just the solving of the quadratic equation to find the two distinct roots (points where the parabola intersects the X axis).