B$.$ Cylindrical pair

C$.$ Screw pair

D$.$ Flat pair

The position of slider is $RC=20$i inch. The length for bar $1$ and $3$ are $13$ and $7$ inch, then angle $$ is $?$

A$.0$

B$.1$

C$.2$

D$.3$

Grashof's Law states:

A$.$ The sum of the shortest link and the medium$-$length link is less than the sum of the longest link and the remaining link.

B$.$ The sum of the shortest link and the medium$-$length link is greater than the sum of the longest link and the remaining link.

C$.$ The sum of the shortest link and the longest link is less than the sum of the mediumlength link and the remaining link.

D$.$ None of the above are correct.

$(3)$ Problem $(50$pts$)$

Consider the following four$-$bar linkage system. The lengths of the linkages are given as follows: $r_1=13$ inches, $r_2=5$ inches, $r_3=20$ inches, and $r_4=11$ inches. The angle ${}_2$ is set at $108.$ Calculate the corresponding angles ${}_3$ and ${}_4$ for both the open and crossed postures of the linkage. You can solve it by either graphical solution or amalvical solution. $(15$ pts$)$