Given the partition $\{0,\frac{1}{4},\frac{1}{2},\frac{3}{4},1\}$, find $L(P)$ and $U(P)$ for the integral $]\int_0^12x\,dx$.

Problem: 

Given the partition $\{0,\frac{1}{4},\frac{1}{2},\frac{3}{4},1\}$, find $L(P)$ and $U(P)$ for the integral $]\int_0^12x\,dx$.

Answer: 

$L(P)=\frac{3}{4}$ and $U(P)=\frac{5}{4}$