$1/$ given the function f$($x$)=$x$^2+20<$ and $=$ to x $<$ and $=2$ a$/$ evaluate the rieman sum with n$=4,$ taking the sample points to be the right endpoints.$$ Explain with aid of the diagram what the riemann sum represents. b$/$ evaluate the riemann with n$=4,$ taking the sample points to be left endpoints.$$ Explain with the aid of the diagram what the riemann sum represents.$$ c$/$ use the definition of definite integral $($with right end$-$poiints$)$ to calculate the value of the integral. Use $($n upper and i$=1$ down$)$ i$=[$n$($n$+1)]/2,($n upper and i$=1$ down$)$ i$^2=[$n$($n$+1)(2$n$+1)]/6,($n upper and i$=1$ down$)$ C$=$nC