1969 AMC 12 Question 22

Let $K$ be the measure of the area bounded by the $x$-axis, the line $x=8,$ and the curve defined by

$$
\begin{aligned} f=\{(x,y)\mid{}&\\ y&=x\\ &\text{when }0\le x\le5,\\ y&=2x-5\\ &\text{when }5\le x\le8\}. \end{aligned}
$$

Then $K$ is: