I think 4! x 3! x 2! x 3!/9 which is 24x2x2x2 which is 24x8 do the calculation yourself
ratio of people: 5/6
ratio of work time: 6/5 = x/x-4
x = 24so 4 days - 25 more people
I agree - 2^2 is 4, by the way
wait, you made a error - you need to subtract the 6 ways all four are together 3 times, as that was quadruple counted
use similar triangles - x/1-x = 3-x/x, x^2 = 3-4x+x^2, x = 3/4
hope that helps!
