a. ta có \(\left|x-386\right|+\left|x-389\right|=\left|x-386\right|+\left|389-x\right|\ge\left|x-386+389-x\right|=3\)
\(\Rightarrow D\le2015-5\times3=2000\)
b. ta có \(\left|x-30\right|+\left|x-4\right|=\left|30-x\right|+\left|x-4\right|\ge\left|30-x+x-4\right|=26\)
\(\Rightarrow E\le\frac{51350}{26}=1975\)