$(4$ points each$)$ The figure below shows the graphs of $f(x)=2\sqrt[\phantom{2}]{x},g(x)=\frac{x^2}{4},y=4,$ and $x=4.$ Also shown are regions $R_1,R_2,$ and $R_3.$ Use the figure to answer the following questions. In each case set$-$up your integral answer but do not evaluate it$.$

a$.$ Set up the integral or integrals to find the area o the region $R_1.$

b$.$ Without using absolute value set up the integral or integrals needed to find the area between $f(x)$ and $g(x)$ for $0x7.$

c$.$ Set up the integral or integrals needed to find the volume formed by rotating $R_3.$ about the x $-$axis.