There are 6 different singers who each sing two songs out of aset of 12 different songs.
This month Singer A sings songs 1 and 2, B sings 3 and 4, C sings 5and 6, D sings 7 and 8, E sings 9 and 10, and singer F sings songs11 and 12.
Find the number of possible assignments next month of two songs tovarious singers (so that all songs are sung)
in which each singer sings at least one different song from the twosongs he/she sang this month.