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A line intersects the x- axis at the point $(1,0)$ and the y- axis at the point $(0,3)$, and has an equation of:

$$\frac{x}{a}+\frac{y}{b}=1$$

What are $a$ and $b$?

$a=3$, $b=1$

$a=1$, but $b$ cannot be determined

$b=1$, but $a$ cannot be determined

$a=1$, $b=3$

$a=2$, $b=2$

Neither $a$ nor $b$ can be determined