For the beam below, take $P=5k,w=1\mathrm{.}5klf,a=3ft.$ The beam is made of steel with $E=29000-$ksi and the moment of inertia $l=76\mathrm{.}8-i{n}^4.$

The moment diagram between A and $C$ is a

horizontal line that coincides with the $x-$axis

concave curve of $2$ nd degree

horizontal line below the $x$ axis

concave curve of $3$rd degree

straight line with a negative slope

straight line with a positive slope

convex curve of $2$nd degree

horizontal line above the $x$ axis

convex curve of $3$rd degree