`a, A = (-17)/23 xx (-29)/53`
`= (-17xx-29)/(23xx53)`
`= 493/1219`
`b, B = (-2/3) xx (-7/11) xx (-13/37)`
`= (-2xx-7xx-13)/(3xx11xx37)`
`= -182/1221`
`c, C = -4/11 . -3/11 . ... . 3/11 . 4/11`
`= -4/11 . -3/11 . ... . 0/11. 1/11 . 2/11 . 3/11 . 4/11`
`= 0`.