`B= 1/1.5 + 1/5.9 + ... + 1/2016.2020`
`⇒ B = 1/4 . (4/1.5 + 4/5.9 +...+ 4/2016.2020)`
`⇒ B = 1/4 . (1 - 1/5 + 1/5 - 1/9 +...+ 1/2016 - 1/2020)`
`⇒ B = 1/4 . (1 - 1/2020)`
`⇒ B = 1/4 . 2019/2020 = 2019/8080`
`C= 1/10.12 + 1/12.14 +...+ 1/998.1000`
`⇒ C = 1/2 . (2/10.12 + 2/12.14 +...+ 2/998.1000)`
`⇒ C = 1/2 . (1/10 - 1/12 + 1/12 - 1/14 +...+ 1/998 - 1/1000)`
`⇒ C = 1/2 . (1/10 - 1/1000)`
`⇒ C = 1/20 - 1/2000 = 99/2000`
