Geometrical Drawing Given are a circumference $(C, r)$, a point $P$, a line $S$ and a length $D$. Determine a line $T$ that passes through $P$ and has intersection with circumference at the points $A$ and $B$ so that the sum of the distances of $A$ and $B$ to the line $S$ is equal to $D$.
Could someone help me with this please?
 A: Problem
Given point $P$, the circunference $\Gamma$ whose center is point $C$ and whose radius is $r$ and the length $D$, find out the line $t$, such that $P \in t$, $\Gamma \cap t  = \{A, B\}$ and $d(A,s)+d(B,s)=D$. See fig.1.

Figure $1$
Solution
(See fig. 2.)

Figure $2$


*

*Draw the line $s'$ such that $s' \parallel s $, $d(s,s')= \frac{D}{2}$ and $s' \cap \Gamma \neq \emptyset$.

*Draw the line segment $CP$ and mark its midpoint $M$ on it.

*Draw the circunference $\Lambda$ whose center is $M$ and whose radius is $CM$.

*Find out the point $N$, such that $\{N\}=s' \cap \Lambda$ and $N$ is inside the circle delimited by $\Gamma$.

*Draw the line $t$, such that $N \in t$ and $P \in t$.

*Find out the points $A$ and $B$, such that $\{A,B\}= t \cap \Gamma$.
Explanation
Note that $N$ is the midpoint of $AB$ and $\angle CNA = \angle CNP = \frac{\pi}{2}$.
As $N$ is midpoint of $AB$, we have:
$$d(A,s)+d(B,s)= 2d(N,s) \Rightarrow$$
$$d(A,s)+d(B,s)= 2 \left(\frac{D}{2}\right) \Rightarrow$$
$$d(A,s)+d(B,s)= D$$
