Figure $2-6$

$$

A production possibilities frontier graph shows Civilian Goods on the horizontal axis and Military goods on the vertical axis. There are two PPFs shown on the graph. PPF sub $1$ is concave to the origin. There are two points noted on PPF sub $1$: $?$ Point A lies between the vertical intercept and point B $?$ Point B lies between point A and the horizontal intercept. PPF sub $2$ lies to the right of PPF sub $1$ and is a straight downward$-$sloping line. There are two points noted on PPF sub $2$: $?$ Point C lies between the vertical intercept and point D $?$ Point D lies between point C and the horizontal intercept. A fifth labeled point lies between the two PPFs and it is labeled point F$.$ Note that Point C lies directly above point A$,$ and point D lies directly to the right of point B$.$

$$

$$

Refer to Figure $2-6.$ Which graph depicts a technological improvement in the production of good Y only?

a$.(1)$

b$.(4)$

c$.(2)$

d$.(3)$