In the figure, rigid bar ABC is support by a pin at $B$

and by post $(1)$ at $A.$ However, there is a gap of

$=10mm$ between the rigid bar at A and post

$(1).$ After load $P$ is applied to the rigid bar, point $C$

moves left by $7$ mm $.$ If the length of post $(1)$ is

$L_1=1\mathrm{.}70m,$ what is the average normal strain

that is produced in post $(1)?$ Use dimensions of

$a=1\mathrm{.}30m$ and $b=0\mathrm{.}65m.$ Use the correct sign

conventions for normal strain.

${}_1=$

$$