The graph shows the relationship between the number of units of item A, $x$, and the number of units of item B, $y$, that can be produced with a fixed amount of resources. The line passes through the points $(0,75)$ and $(50,0)$. If the equation representing this relationship is written in the form $Ax+By=C$, where $A$, $B$, and $C$ are positive integers with no common factors other than 1, what is the value of $C$?