`B=(3²)/(1×4)+(3²)/(4×7)+...+(3²)/(193×196)+(3²)/(196×199)`
`B:3=3/(1×4)+3/(4×7)+...+3/(193×196)+3/(196×199)`
`B:3=(4-1)/(1×4)+(7-4)/(4×7)+...+(196-193)/(193×196)+(199-196)/(196×199)`
`B:3=4/(1×4)-1/(1×4)+7/(4×7)-4/(4×7)+...+196/(193×196)-193/(193×196)+199/(196×199)-196/(196×199)`
`B:3=1-1/4+1/4-1/7+...+1/193-1/196+1/196-1/199`
`B:3=1-1/199`
`B:3=189/199`
`B=594/199`